UNIVERSE
made of an infinite amount of space,
matter and time.
the start of the universe, the universe
has no beginning and no end; perhaps
the same photons that have always been
in the universe continue to move in the
space that has always been.
particles of light humans have named
"photons". Photons are the base unit
of all matter from the tiniest
particles to the largest galaxies.
The basic order of matter from smaller
to largest is photons, electrons,
positrons, muons, protons, neutrons,
atoms, molecules, living objects,
planets, stars, globular clusters,
galaxies, galaxtic clusters.
meters every second in a line, but as
pieces of matter, can be slightly
slowed from the force of gravity, and
stop for an instant when they collide.
Photons
move 300 million meters every second in
a line but as pieces of matter their
velocity changes slightly because of
gravity, and theoretically photons
bounce off each other, at which time
they come to a complete stop relative
to the rest of the universe for an
instant before bouncing and
accelerating away from each other in
the opposite direction.
and so photons form structures such as
protons, atoms, molecules, molecule
groups (like all of life of earth),
planets, stars, galaxies, and clusters
of galaxies.
Gravity is responsible for photons
forming Hydrogen, Hydrogen forming
nebulas, nebulas forming stars, and
stars forming galaxies.
galaxies we can see are only a tiny
part of the universe. Most of the
galaxies in the universe we will never
see because they are too far away for
even 1 particle of light from them to
be going in the exact direction of our
tiny location, or are captured by atoms
between here and there.
One estimate
has 70e21 (sextillion) stars in only
the universe we can see. That is 10
times more stars than grains of sand on
all the earth.
clear. Photons form gas clouds of
Hydrogen and Helium, these gas clouds,
called nebuli condense to form galaxies
of stars. The stars emit photons back
out into the rest of the universe,
where they collect and form clouds
again. Around each star are many
planets and pieces of matter. On many
of those planets intelligent life
evolves. This life moves their stars
out of spiral galaxies to form globular
clusters, and ultimately to transform
spiral galaxies into elliptical
galaxies that travel the universe
looking for more matter to fuel their
movement.
It may very well be that stars at this
scale are photons, spiral galaxies
charged particles, globular galaxies
neutral particles, and galactic
clusters atoms at a much larger scale
in an infinite macro and micro scale.
the most distant galaxies we can see
have a lower frequency may be due to
the effects of gravitation and/or
particle collision in the large
distance between source and observer.
from a gas cloud that formed by
capturing matter in the form of light
from other stars, from the remains of a
previously destroyed galaxy, or some
combination of the two.
eventually orbit forms, perhaps in a
nebula, when matter in the nebula
starts accumulating and rotating as a
result of gravity, or from the remains
of an exploded star that condensed
again under the influence of gravity.
My
opinion is that stars contain molten
iron in their center, similar to the
earth. {check with supernova remnants}
The density of the star the earth
rotates is similar to that of a liquid.
The most popular theory to explain how
stars give off so many photons is that
these photons exit as a result of
Hydrogen atomically fusing into Helium,
and I want to add my opinion that
potentially the pressure of gravity
simply separates atoms of Hydrogen and
helium into their source photons.
Perhaps the reaction is similar to the
center of the earth where red hot
liquid iron emits photons. We
obviously do not explain that red hot
molten metal as being the result of
nuclear fusion, but yet it is clearly
not oxygen combustion. Clearly there
are many photons exiting stars every
second, and each star is losing large
amounts of matter in the form of
photons. In addition, the most popular
theory explains that most atoms heavier
than Hydrogen and no heavier than Iron
are made in stars, and atoms larger
than iron can only be made in
supernovae.
The current view theorizes
that the iron is made just before the
supernova, in the gravitational
collapse, but I find a liquid iron core
being there for the lifetime of every
star as a more logical explanation.
move closer to the center and lighter
atoms are sent farther out.
Terrestrial planets are red hot, have
surface of melted rock, all lighter
atoms float to the surface of the
molten planets. All the H2O from the
first earth oceans and lakes is in the
atmosphere in gas form.
ways:
1) spherical planet collides with
earth, moon forms from remaining matter
in ring around earth.
2) spherical planet is
caught in earth orbit
3) moon of earth forms
naturally from original matter of star
system in orbit around earth.
The Moon
orbiting 5 degrees from the axis of the
Earth's orbit implies that the Moon was
captured, although 5% is not a
particularly large difference from the
plane of the Earth's rotation. That the
Moon orbits in the same direction as
the Earth is evidence in favor of the
Moon forming around the Earth.
4,571 million years old.
[1] The ''Zag'' meteorite fell to Earth
in 1988 COPYRIGHTED
source: http://news.bbc.co.uk/1/hi/sci/t
ech/783048.stm
Apollo missions (4.53 billions old).
[1]
http://www.nasm.si.edu/exhibitions/attm/
atmimages/S73-15446.f.jpg
http://www.nasm.si.edu/exhibitions/attm/
nojs/wl.br.1.html
source:
earth) rocks date from this time 4.5
billion years before now.
LIFE
cools into thin crust, H2O condenses
from the atmosphere by raining, filling
the lowest parts of land to make the
first earth oceans, lakes, and rivers.
meteorite) zircon yet found on earth,
4.404 billion years old, from Gneiss in
West Australia, is evidence that the
crust and liquid water were on the
surface of earth 4.4 billion years
before now.
[1]
http://www.geology.wisc.edu/zircon/Earli
est%20Piece/Images/8.jpg
source:
sugars, the components of living
objects are created on earth. These
molecules are made in the oceans, fresh
water, and or atmosphere of earth (or
other planets) by lightning, photons
with ultraviolet frequency from the
star, or ocean floor volcanos.
nucleotides), proteins (polymers made
of amino acids), carbohydrates
(polymers made of sugars) and lipids
(glycerol attached to fatty acids)
evolved is not clearly known.
Some proteins and nucleic acids have
been formed in labs by using clay which
can dehydrate and which provides long
linear crystal structures to build
proteins and nucleic acids on. Amino
acids join together to form
polypeptides when an H2O molecule is
formed from a Hydrogen (H) on 1 amino
acid and a hydroxyl (OH) on the second.
Are all proteins, carbohydrates, lipids
and DNA the products of living objects?
Is RNA the only molecule of these that
was made without the help of living
objects?
The most popular theory now has RNA
(and potentially lipids) evolving first
before any living objects.
There is still a large amount of
experiment, exploration and education
that needs to be done to understand the
origins of living objects on planet
earth. My opinion is that as soon as
there was liquid water on the earth,
4.4 billion years before now, as zircon
crystals show, the construction of
living objects started on earth.
Perhaps RNA molecules, called
"ribozymes" evolved which can make
copies of RNA, by connecting free
floating nucleotides that match a
nucleotide on the same or a different
RNA, without any proteins. But until
such ribozyme RNA molecules are found,
the only molecule known to copy nucleic
acids are proteins called polymerases.
If such ribozymes exist, then one of
the first coded instructions on the RNA
molecule that was the ancestor of every
living species, must have been the code
to make this ribozyme.
These early RNA molecules
may have been protected by liposomes
(spheres of lipids).
This process of RNA (and then later
DNA) duplication is the most basic
aspect of life on earth, and for all
the diversity, the one common element
of all life is this constant process of
DNA duplication, which will later
evolve to include cell division. This
starts the unbroken thread of copying
and division that connects the earliest
ancestor, some RNA molecule, to all
life on earth that has ever lived.
creation of various Transfer RNA (tRNA)
molecules.
Random mutations in the copying (and
perhaps even in the natural formation)
of RNA molecules probably created a
number of the necessary tRNAs (transfer
RNA, an RNA molecule responsible for
matching free floating amino acid
molecules to 3 nucleotide sequences on
other RNA molecules).
This would be a precellular protein
assembly system, where tRNA (transfer
RNA) molecules can build polypeptide
chains of amino acids by linking
directly to other RNA strands.
Part of each tRNA molecule bonds with a
specific amino acid, and a 3 nucleotide
sequence from a different part of the
tRNA molecule bonds with the opposite
matching 3 nucleotide sequence on an
(m)RNA molecule.
Since there are tRNA molecules for each
amino acid (although some tRNAs can
attach to more than one amino acid?),
there must have been a slow
accumulation of various tRNA molecules
for each of the 20 amino acids used in
constructing polypeptides in cells
living now. Perhaps after the
evolution of the first tRNA, the first
polypeptides were chains of all the
same one amino acid. With the
evolution of a second tRNA polypeptides
would have more variety because now two
amino acids would be available to build
polypeptides.
This polypeptide assembly system may
exist freely in water, or within a
liposome. This sytem builds many more
proteins than would be built without
such a system. The mRNA with the code
to make copier RNA, now also contains
the code to produce various tRNA
molecules. These molecules function as
a unit, and proto-cell, with the rest
of the mRNA initially containing random
codes for random proteins.
For the first time, RNA code represents
a template for other RNA molecules, but
also a template for building proteins
with the help of tRNA molecules.
There is some question of where the
origin of the first cell took place,
near volcanos on the ocean floor, or in
fresh water lakes and tidal pools near
volcanos on land, because unprotected
nucleic acids cannot exist for much
time in the ocean because of Sodium and
Chlorine.
What were the first amino acids
connected as proteins? Were the first
proteins all made with the same amino
acid?
Ribosomal RNA moves down mRNA molecules
functioning as a platform for bringing
the mRNA and tRNA molecules together to
assemble polypeptides (proteins).
This rRNA serves as an early ribosome;
objects that serve as sites for
building polypeptides and are found in
every cell. As time continues the
ribosome will grow to include two more
RNA molecules, some protein molecules,
and a second half that will make
polypeptide construction more
efficient.
The rRNA serves the purpose of bringing
amino acids close enough to bond with
each other to form polypeptides.
As an rRNA moves down an mRNA, tRNA
molecules bond with the mRNA and on the
opposite side of the tRNA, a matching
amino acid (separates? from the tRNA
and) attaches to a growing polypeptide
chain.
Now the mRNA that is the
ancestral/progenitor of all of life,
contains the code for the copier RNA,
tRNAs, and the rRNA molecule. These
nucleic acids function as a unit, and
proto-cell.
importance is built, an RNA polymerase.
A molecule that can more efficiently
copy RNA.
The first protein of real
importance is evolved by RNA and
assembled by the early ribosome, an RNA
polymerase. A molecule that can more
efficiently copy RNA.
is built by the early ribosome protein
making protocell. This protein changes
ribonucleotides into
deoxyribonucleotides. This allows the
first DNA molecule on earth to be
assembled.
Ribonucleotide reductase may be the
molecule that allowed DNA to be the
template for the line of cells that
survived to now.
to copy DNA by assembling DNA
nucleotides from other DNA molecules.
causes the early ribosome to create
reverse transcriptase, a protein that
can assemble DNA molecules from an RNA
molecule template.
With this advance, a DNA molecule can
be constructed that has all of the code
that was stored on the long evolved RNA
molecule. DNA now serves as a more
stable template for making mRNA, each
tRNA, rRNA, and the RNA and DNA
polymerases.
RNA polymerase proteins build RNA
molecules using the new DNA template,
that still perform their original
polypeptide building function together
with the tRNA and rRNA molecules, but
are labeled "mRNA" (Messenger RNA)
because they move from DNA to ribosome.
Why DNA
serves as the template for all cells
and not mRNA is not fully understood,
but DNA is a more stable molecule than
the single stranded RNA. Perhaps the 2
legs of DNA serve some other important
reasons, for example, two legs may
allow two processes to happen at one
time.
around DNA, made of proteins. This
membrane holds water inside a cell.
This is the first cell. rRNA
comparison shows that this is most
likely a eubacterium.
DNA produces instructions for
cytoplasm, the cytoplasm is assembled
from proteins made by the ribosome.
For the first time, DNA and ribosomes
are building cell structure. The
templates for each tRNA, rRNA, mRNA and
DNA polymerase proteins are already
coded in a central strand of DNA. DNA
protected by cytoplasm is more likely
to survive and copy. This cell is
heterotrophic and has no metabolism to
produce ATP. Amino acids, nucleotides,
H2O, and other molecules enter and exit
the cytoplasm only because of a
difference in concentration from inside
and outside the cell (passive
transport) and represent the beginnings
of the first digestive system. This
either happens in fresh water lakes or
in salty oceans, perhaps near lava
vents on or under the ocean floor. As
this line of DNA continues to make
copies of itself, all copies now have
cytoplasm. The DNA is composed mainly
of instructions to assemble the nucleic
acids and proteins needed to build
ribosomes, polymerases and cytoplasm.
This cell structure forms the basis of
all future cells of every living object
on earth. These first cells are
anaerobic (do not require free oxygen)
and heterotrophic, meaning that they do
not make their own food: amino acids,
nucleotides, phosphates, and sugars.
These bacteria depend on these
molecules and photons in the form of
heat to reproduce and grow.
A system of division must evolve which
attaches the original and newly
synthesized copy of DNA to the
cytoplasm, so that as the cell grows,
the two copies of DNA can be separated
and the first membraned cells can
divide into two cells. This is the
beginning of the "binary fission"
method of cell division. Division of
the cell begins with the division of
the DNA membrane-attachment site and
separates by the growth of new
cytoplasm.
DNA has 2 functions, 1) to be copied
by the polymerase protein, 2) to serve
as a code for assembling proteins.
Two
important evolutionary steps evolve:
DNA duplication in cytoplasm, and cell
(DNA with cytoplasm) division.
The process of DNA duplication is
probably similar if not the same
process using the same proteins that
were used to duplicate DNA without
cytoplasm.
circle allows the DNA polymerase to
make continuous copies of the cell.
In
theory prokaryote cells do not
deteroiate from the effect of aging,
but they do endure mutations (from
photons with ultraviolet frequency, for
example), however, there are many other
ways prokaryotes can be destroyed (loss
of water, physically damaged by
nonliving objects, eaten by other
organisms, and other mechanisms).
molecules into and out of the cytoplasm
(facilitative diffusion) evolve.
[1] Uniporters are transport proteins
that transport a substance across a
membrane down a concentration gradient
from an area of greater concentration
to lesser concentration. The transport
is powered by the potential energy of a
concentration gradient and does not
require metabolic energy.
source: http://www.cat.cc.md.us/~gkaiser
/biotutorials/eustruct/cmeu.html
[2] Channel proteins transport water
or certain ions down a concentration
gradient from an area of higher
concentration to an area of lower
concentration. In the case of water,
the channel proteins are called
aquaporins. Water molecules are small
enough that they can also pass between
the phospholipids in the cytoplasmic
membrane by passive diffusion.
source:
from bacteria, or are initially
bacteria. These cells depend on the
DNA duplicating and protein producing
systems of other cells to reproduce
themselves. Over time, more effective,
and efficient virus designs will
survive.
cytoplasm. Cells can now make ATP from
glucose and eventually other
monosaccharides, the end product is
pyruvate.
The glycolysis equation is:
C6H12O6
(glucose) + 2 NAD+ + 2 ADP + 2 P
-----> 2 pyruvic acid, (CH3(C=O)COOH +
2 ATP + 2 NADH + 2 H+
cytoplasm. Cells (all anaerobic) can
now make more ATP and convert pyruvate
(the final product of glycolysis) to
lactate (an ionized form of lactic
acid).
evolves in the cytoplasm. Cells (all
anaerobic) can now convert pyruvate
(the final product of glycolysis) to
ethanol.
that can assemble lipids.
metabolism (ATP) to transport molecules
into and out of the cytoplasm (active
transport) evolve.
[1] TP: not clear what the red circles
are, some kind of molecule I
guess. Antiporters are transport
proteins that simultaneously transport
two substances across the membrane in
opposite directions; one against the
concentration gradient and one with the
concentration gradient. Antiporters
typically use proton motive force to
transport a substrate across the
membrane. The movement of protons
across the membrane (proton motive
force) provides the energy for
transporting the substrate across the
membrane against its concentration
gradient..
source: http://www.cat.cc.md.us/~gkaiser
/biotutorials/eustruct/cmeu.html
[2] Symporters are transport proteins
that simultaneously transport two
substances across the membrane in the
same direction; one against the
concentration gradient and one with the
concentration gradient. Symporters
often use proton motive force to
transport a substrate across the
membrane. The movement of protons
across the membrane (proton motive
force) provides the energy for
transporting the substrate.
source:
be created with an early precellular
protein production system must have
been a protein (like RNA polymerase)
that can make copies of RNA from mRNA
molecules. This protein may have
outperformed a ribozyme that was
performing the copying function.
Eventually mRNA that coded for tRNA
molecules and mRNA that coded for rRNA
molecules merged to form a template.
Now the entire protein production
system (the mRNA itself, tRNAs, rRNAs,
and the RNA polymerase) could be copied
many times by the RNA polymerase
protein.
This is before cytoplasm or any cell
wall has evolved. RNA and DNA copying
happens in water, the first cell has
not evolved yet.
evolves in prokaryotes. Now some
prokaryotes can exchange circular
pieces of DNA (plasmids), through tubes
(pili). Conjugation may be the process
that led to sex (cellular fusion) and
also the transition from a circle of
DNA to chromosomes in eukaryotes, since
some protists (cilliates and some
algae) reproduce sexually by
conjugation.
Archaeal flagellins are related to
members of the type IV pilin/transport
superfamily widespread in bacteria.
In addition
to pili and conjugation, proteins
evolve that can assist in splitting DNA
and also proteins that assist in
merging two strands of DNA together,
since some times the DNA in split and
the new plasmid is connected and the
DNA circle is sown back together.
[1] the fertility factor or F factor is
a very large (94,500 bp) circular dsDNA
plasmid; it is generally independent of
the host chromosome. COPYRIGHTED
source: http://www.mun.ca/biochem/course
s/3107/images/Fplasmidmap.gif
[2] conjugation (via pilus)
COPYRIGHTED EDU
source: http://www.bio.miami.edu/dana/16
0/conjugation.jpg
Perhaps pili
evolved into flagella, flagella into
pili, or the two systems are
unrelated.
Proteins in Archaebacteria flagella are
related to pili in bacteria.
This may be the beginning of motility.
Now for the first time, cells are not
completely controlled by surrounding
matter, but can make limited choices
about their location.
allow certain proteins coded by DNA to
not be built, evolve. Proteins bind
with these DNA sequences to stop RNA
polymerase from building mRNA molecules
which would be translated into
proteins. Operons allow a bacterium to
produce certain proteins only when
necessary. Bacteria before now can
only build a constant stream of all
proteins encoded in their DNA.
eubacteria.
Without bacteria that convert N2 into
nitrogen compounds, the supply of
nitrogen necessary for much of life
would be seriously limited and would
drastically slow evolution on earth.
Nitrogen
fixation is the process by which
nitrogen is taken from its relatively
inert molecular form (N2) in the
atmosphere and converted into nitrogen
compounds useful for other chemical
processes (such as, notably, ammonia,
nitrate and nitrogen dioxide).
Nitrogen fixation is performed
naturally by a number of different
prokaryotes, including bacteria, and
actinobacteria certain types of
anaerobic bacteria. Many higher plants,
and some animals (termites), have
formed associations with these
microorganisms.
The best-known are legumes (such as
clover, beans, alfalfa and peanuts,)
which contain symbiotic bacteria called
rhizobia within nodules in their root
systems, producing nitrogen compounds
that help the plant to grow and compete
with other plants. When the plant dies,
the nitrogen helps to fertilize the
soil. The great majority of legumes
have this association, but a few genera
(e.g., Styphnolobium) do not.
[1] This is an image of nitrogen cycle
taken from this [1] EPA website. PD
source: http://en.wikipedia.org/wiki/Ima
ge:Nitrogen_Cycle.jpg
filment growth evolves in prokaryotes.
Cyanobacteria
grow in filaments.
Unlike eukaryotes, there is no
communication between cells in
prokaryote filments.
prokaryotes evolve. Heterocysts evolve
in cyanobacteria.
Heterocysts are specialized
nitrogen-fixing cells formed by some
filamentous cyanobacteria during
nitrogen starvation.
What cell differentiation is
first is unknown, perhaps cells that
form spores, or cysts, or perhaps cell
differentiation that is observes in
cyanobacterial filamentous cells.
Heterocysts are specialized
nitrogen-fixing cells formed by some
filamentous cyanobacteria, such as
Nostoc punctiforme and Anabaena
sperica, during nitrogen starvation.
They fix nitrogen from dinitrogen (N2)
in the air using the enzyme
nitrogenase, in order to provide the
cells in the filament with nitrogen for
biosynthesis. Nitrogenase is
inactivated by oxygen, so the
heterocyst must create a microanaerobic
environment. The heterocysts' unique
structure and physiology requires a
global change in gene expression. For
example, heterocysts:
* produce three additional cell
walls, including one of glycolipid that
forms a hydrophobic barrier to oxygen
*
produce nitrogenase and other proteins
involved in nitrogen fixation
* degrade
photosystem II, which produces oxygen
* up
regulate glycolytic enzymes, which use
up oxygen and provide energy for
nitrogenase
* produce proteins that scavenge
any remaining oxygen
Cyanobacteria usually obtain a fixed
carbon (carbohydrate) by
photosynthesis. The lack of photosystem
II prevents heterocysts from
photosynthesising, so the vegetative
cells provide them with carbohydrates,
which is thought to be sucrose. The
fixed carbon and nitrogen sources are
exchanged though channels between the
cells in the filament. Heterocysts
maintain photosystem I, allowing them
to generate ATP by cyclic
photophosphorylation.
Single heterocysts develop about every
9-15 cells, producing a one-dimensional
pattern along the filament. The
interval between heterocysts remains
approximately constant even though the
cells in the filament are dividing. The
bacterial filament can be seen as a
multicellular organism with two
distinct yet interdependent cell types.
Such behaviour is highly unusual in
prokaryotes and may have been the first
example of multicellular patterning in
evolution. Once a heterocyst has
formed, it cannot revert to a
vegetative cell, so this
differentiation can be seen as a form
of apoptosis. Certain
heterocyst-forming bacteria can
differentiate into spore-like cells
called akinetes or motile cells called
hormogonia, making them the most
phenotyptically versatile of all
prokaryotes.
The mechanism of controlling
heterocysts is thought to involve the
diffusion of an inhibitor of
differentiation called PatS. Heterocyst
formation is inhibited in the presence
of a fixed nitrogen source, such as
ammonium or nitrate. The bacteria may
also enter a symbiotic relationship
with certain plants. In such a
relationship, the bacteria do not
respond to the availability of
nitrogen, but to signals produced by
the plant. Up to 60% of the cells can
become heterocysts, providing fixed
nitrogen to the plant in return for
fixed carbon.
The cyanobacteria that form heterocysts
are divided into the orders Nostocales
and Stigonematales, which form simple
and branching filaments respectively.
Together they form a monophyletic
group, with very low genetic
variability.
[1] Anabaena COPYRIGHTED EDU
source: http://home.manhattan.edu/~franc
es.cardillo/plants/monera/anabaena.gif
[2] Anabaena smitthi COPYRIGHTED
FRANCE
source: http://www.ac-rennes.fr/pedagogi
e/svt/photo/microalg/anabaena.jpg
can produce some if not all of their
own food (amino acids, nucleotides,
sugars, phophates, lipids, and
carbohydrates), but require phosphorus,
nitrogen, CO2, water and light in the
form of heat.
There are only 2 kinds of autotrophy:
Lithotrophy and Photosynthesis. These
are lithotrophic cells that change
inorganic (abiotic) molecules into
organic molecules. These cells are
archaebacteria, called methanogens that
perform the reaction: 4H2 + CO2 -> CH4
+ 2H2O. They convert CO2 into Methane.
Methane is better than CO2 for
trapping heat, and could have
contributed to heating the earth.
cells only have Photosystem I.
Photosynthesis Photosystem I evolves in
early anaerobic prokaryote cells. One
of two photosythesis systems,
photosystem I uses a pigment
chlorophyll A, absorbs photons in 700
nm wave lengths best, breaking the bond
betwenn H2 and S. They are anaerobic
and perform the reaction: H2S
(Hydrogen Sulfide) + CO2 + light ->
CH2O (Formaldehyde) + 2S.
Only 5 phyla of
eubacteria can photosynthesize.
evolves in early prokaryote cells.
Photosystem 2 absorbs photons best at
680nm wavelengths, a higher frequency
of light than Photosystem I. These
cells can break the strong Hydrogen
bonds between Hydrogen and Oxygen in
water molecules (more abundant than
Sulphur). This system emits free
Oxygen.
The simple equation of photosynthesis
is: 6 H2O + 6 CO2 + photons = C6H12O6
(glucose) + 6O2. The detailed steps of
photosynthesis are called the "Calvin
Cycle". Prokaryote cells can now
produce their own glucose to store and
be converted to ATP by glycolysis and
fermentation later.
This sytem is the main system
responsible for producing the Oxygen
now in the air of earth.
Of the 5 phyla of
eubacteria that can photosynthesize,
only 1, cyanobacteria, produces oxygen.
the "Citric Acid Cycle", and the "Krebs
Cycle") evolves, probably in
cyanobacteria, as a substitute for
fermentaton, by using oxygen to break
down the products of glycolysis,
pyruvic acid, to CO2 and H2O, producing
18 more ATP molecules.
This is the
first aerobic cell, a cell that has an
oxygen based metabolism. This cell
uses oxygen to convert glucose (and
eventually other sugars and fats) into
CO2, H2O and ATP. For example, cells
that oxidize glucose perform the
reaction:
C6H12O6 + 6 O2 + 38 ADP + 38 phosphate
-> 6 CO2 + 6 H2O + 38 ATP
This reaction
(with glycolysis) can produce up to 36
ATP molecules. Cellular respiration is
the opposite (although the specific
reactions differ) of photosynthesis
which starts with H2O and CO2 and
produces glucose.
Steps are:
Glycolysis preparatory
phase
Glycolysis pay-off phase
Oxidative
carboxylation
Krebs cycle
[1] kreb cycle from
http://people.unt.edu/~hds0006/tca/
source:
for a cell wall. The cell wall only
protects bacteria and does not filter
any molecules as the cytoplasm does.
is
first gram-negative cell wall?
1. Only contain a few layers of
peptidoglycan -- the building block for
strong, rigid cell walls
2. Contain an
outer membrane, external to the
peptidoglycan, called the
lipopolysaccharide
3. The space between the layers of
peptidoglycan and the secondary cell
membrane is called periplasmatic space
4.
The S-layer is directly attached to the
outer membrane, rather than the
peptidoglycan
5. Any flagella, if present, have 4
supporting rings instead of two
6. No
teichoic acids are present"
[1] one is indirectly
from http://www.cvm.uiuc.edu/courses/vp
331/index.html
source: file:/root/web/Structures_in_pat
hogenesi1.html
source: http://www.mansfield.ohio-state.
edu/~sabedon/biol1080.htm
secondary processes in cells that are
not fully understood yet.
to be found, more DNA needs to be
sequenced, and more bacteria found and
grown to fully understand when bacteria
parts evolved. For example:
flagella
plasmids
pili and "conjugation" the trade of
pieces of plasmid DNA (this may be the
earliest form of sex {or syngamy})
changing into
spores
When gram-stain positive cell walls
evolved.
When the various shapes evolved:
spherical
(coccus,cocci)
rod (bacillus,bacilli)
spiral (spirilla)
other:
short rods (coccobacilli).
commas (vibrii).
squares (rare)
stars (rare)
irregula
r (rare)
Which specific bacteria of the Archaea
(if any) were first, which of the
Eubacteria and Cyanobacteria came
next.
When the "Nitrogen Cycle" or "Nitrogen
Fixing" evolved. Few cells can
separate N2 into N, (needed for nucleic
acids?). The waste product urea is
converted by one bacteria to ammonia, a
second bacteria converts the ammonia to
N2.
estimates of when the first Eubacteria
and Archaea evolved. Eubacteria and
Archaea (also called Archaebacteria)
are the two major lines of Prokaryotes.
Prokaryotes are the most primitive
living objects ever found. In contrast
to the later evolved Eukaryotes,
Prokaryotes have a circle of DNA
located in their cytoplasm (not
chromosomes) and have no nucleus. At
least one genetic comparison shows
Eubacteria and Archaea evolving now.
After the full genomes of all living
species are known, and understood we
will have more certainty about the
history of evolution. Many genetic
trees are based on DNA genes (sequences
of DNA that define nucleic acids or
proteins). In particular the genes for
ribosomal RNA are thought to be very
conserved over time, although perhaps
genes for reproduction, or cytoplasm,
for example may later prove to be more
conserved over time.
Only when the full
genomes of all living species are
known, and understood will we have
strong certainty about the history of
evolution. Many genetic trees are
based on DNA genes (sequences of DNA
that define nucleic acids or proteins),
in particular ribosomal RNA which is
thought to be highly conserved over the
eons of time. Ribosomal RNA may be the
best record of evolutionary history,
but perhaps other genes, for example,
those involved with reproduction, or
cytoplasm will prove to be more
conserved or better estimates of
evolutionary history. For example, I
think the method of reproduction would
be the most conserved, since that
process is the most necessary for
survival, changes to those genes may
stop continued existence, where changes
to rrna may not be as serious. In
addition, the vast diversity and change
in reproductive method over time,
should tell us that similar large scale
changes could have happened for rrna,
cytoplasm, and indeed any part of a
cell.
These early Archaea and Eubacteria are
"thermophile" bacteria, bacteria that
are found and grow best in hot water
(80+ degrees Celsius). That genetic
evidence puts these prokaryotes as the
oldest living prokaryotes is evidence
that the first prokaryotes on earth may
have lived in hot water, perhaps near
thermal springs or near ocean floor
volcanos. Perhaps the water on the
early earth was hot when these first
prokaryotes evolved.
Archaea are similar to
other prokaryotes in most aspects of
cell structure and metabolism. However,
their genetic transcription and
translation are very similar to those
of eukaryotes.
[1] Figure 1) Changing views of the
tree and timescale of life. a) An
early-1990s view, with the tree
determined mostly from ribosomal RNA
(rRNA) sequence analysis. This tree
emphasizes vertical (as opposed to
horizontal) evolution and the close
relationship between eukaryotes and the
Archaebacteria. The deep branching
(>3.5 Giga (109) years ago, Gya) of
CYANOBACTERIA (Cy) and other Eubacteria
(purple), the shallow branching
(approx1 Gya) of plants (Pl), animals
(An) and fungi (Fu), and the early
origin of mitochondria (Mi), were based
on interpretations of the geochemical
and fossil record7, 8. Some deeply
branching amitochondriate (Am) species
were believed to have arisen before the
origin of mitochondria44. Major
symbiotic events (black dots) were
introduced to explain the origin of
eukaryotic organelles42, but were not
assumed to be associated with large
transfers of genes to the host nucleus.
They were: Eu, joining of an
archaebacterium host with a eubacterium
(presumably a SPIROCHAETE) to produce
an amitochondriate eukaryote; Mi,
joining of a eukaryote host with an
alpha-proteobacterium (Ap) symbiont,
leading to the origin of mitochondria,
and plastids (Ps), joining of a
eukaryote host with a cyanobacterium
symbiont, forming the origin of
plastids on the plant lineage and
possibly on other lineages. b) The
present view, based on extensive
genomic analysis. Eukaryotes are no
longer considered to be close relatives
of Archaebacteria, but are genomic
hybrids of Archaebacteria and
Eubacteria, owing to the transfer of
large numbers of genes from the
symbiont genome to the nucleus of the
host (indicated by coloured arrows).
Other new features, largely derived
from molecular-clock studies16, 39 (Box
1), include a relatively recent origin
of Cyanobacteria (approx2.6 Gya) and
mitochondria (approx1.8 Gya), an early
origin (approx1.5 Gya) of plants,
animals and fungi, and a close
relationship between animals and fungi.
Coloured dashed lines indicate
controversial aspects of the present
view: the existence of a
premitochondrial symbiotic event and of
living amitochondriate eukaryotes,
ancestors of which never had
mitochondria. c) The times of
divergence of selected model organisms
from humans, based on molecular clocks.
For the prokaryotes (red), because of
different possible origins through
symbiotic events, divergence times
depend on the gene of interest.
source: http://www.nature.com/nrg/journa
l/v3/n11/full/nrg929_fs.html
[2] Figure 2 A phylogeny of
prokaryotes. The relationships of
selected prokaryote model organisms
based on recent studies14-19. Times of
divergence (million years ago (Mya)
plusminus one standard error) are
indicated at nodes in the tree16, 39.
Branch lengths are not proportional to
time. Phyla and phylum-level groupings
are indicated on the right.
source: http://www.nature.com/nrg/journa
l/v3/n11/full/nrg929_fs.html
evolve.
Genetic comparison shows the Archaea
Phylum, Euryarchaeotes evolving now.
The Euryarchaeota are a major group of
Archaea. They include the methanogens,
which produce methane and are often
found in intestines, the halobacteria,
which survive extreme concentrations of
salt, and some extremely thermophilic
aerobes and anaerobes. They are
separated from the other archaeans
based mainly on rRNA sequences.
Euryarchaeota may contain the most
ancient DNA of any living object on
earth.
PHYLUM Euryarchaeota
CLASS Archaeoglobi
CLASS Halobacteria
CLASS
Methanobacteria
CLASS Methanococci
CLASS Methanomicrobia
CLASS Methanopyri
CLASS
Methanosarcinae
CLASS Thermococci
CLASS Thermoplasmata
[1] tree of archaebacteria (archaea)
COPYRIGHTED
source: http://www.uni-giessen.de/~gf126
5/GROUPS/KLUG/Stammbaum.html
[2] A phylogenetic tree of living
things, based on RNA data, showing the
separation of bacteria, archaea, and
eukaryotes. Trees constructed with
other genes are generally similar,
although they may place some
early-branching groups very
differently, thanks to long branch
attraction. The exact relationships of
the three domains are still being
debated, as is the position of the root
of the tree. It has also been suggested
that due to lateral gene transfer, a
tree may not be the best representation
of the genetic relationships of all
organisms. NASA
source: http://en.wikipedia.org/wiki/Ima
ge:PhylogeneticTree.jpg
evolves.
Genetic comparison shows Archaea
Phylum, Crenarchaeotes evolving now.
The phylum Crenarchaeota, commonly
referred to as the crenarchaea, in the
domain Archaea, contains many extremely
thermophilic and psychrophilic
organisms. They were originally
separated from the other archaeons
based on rRNA sequences, since then
physiological features, such as lack of
histones have supported this division.
Until recently all cultured crenarchaea
have been thermophilic or
hyperthermophilic organisms, some of
which have the ability to grow up to
113 degrees C. These organisms stain
gram negative and are morphologically
diverse having rod, cocci, filamentous
and unusually shaped cells.
PHYLUM
Crenarchaeotes
ORDER Caldisphaerales
ORDER Cenarchaeales
ORDER
Desulfurococcales
ORDER Sulfolobales
ORDER Thermoproteales
[1] tree of archaea ?
source: http://www.uni-giessen.de/~gf126
5/GROUPS/KLUG/Stammbaum.html
[2] Microscopia elettronica a
scansione dell'archeobatterio
termoacidofilo Sulfolobus solfataricus
COPYRIGHT ITALY
source: http://www.area.fi.cnr.it/r&f/n6
/ingrand.htm
Acasta and Great Slave Lake in the
North West territories of Canada dates
from this time, 4030 million years
before now.
source: http://www.regione.emilia-romagn
a.it/geologia/divulgazione/pianeta_terra
/09_paesaggio/img/app/c09_a01_01.jpg
source:
(Aquifex, Thermotoga, etc.) evolve now.
Gene
tic comparison shows that Eubacteria
"Hyperthermophiles" (Aquifex,
Thermotoga, etc.) evolve now.
This may be the living object with the
most primitive DNA found on earth
(depending on the age of the archaea).
This group of eubacteria includes the
Phyla "Aquificae",
"Thermodesulfobacteria", and
"Thermotogae".
The Aquificae phylum is a diverse
collection of bacteria that live in
harsh environmental settings. They have
been found in hot springs, sulfur
pools, and thermal ocean vents. Members
of the genus Aquifex, for example, are
productive in water between 85 to 95
°C. They are the dominant members of
most terrestrial neutral to alkaline
hot springs above 60 degrees celsius.
They are autotrophs, and are the
primary carbon fixers in these
environments. They are true bacteria
(domain eubacteria) as opposed to the
other inhabitants of extreme
environments, the Archaea.
Thermotoga are thermophile or
hyperthermophile bacteria whose cell is
wrapped in an outer "toga" membrane.
They metabolize carbohydrates. Species
have varying amounts of salt and oxygen
tolerance. Thermotoga subterranea
strain SL1 was found in a 70°C deep
continental oil reservoir in the East
Paris Basin, France. It is anaerobic
and reduces cystine and thiosulfate to
hydrogen sulfide.
[1] Aquifex pyrophilus (platinum
shadowed). © K.O. Stetter & Reinhard
Rachel, University of Regensburg.
source: http://biology.kenyon.edu/Microb
ial_Biorealm/bacteria/aquifex/aquifex.ht
m
[2] Aquifex aeolicus. © K.O. Stetter
& Reinhard Rachel, University of
Regensburg.
source: http://biology.kenyon.edu/Microb
ial_Biorealm/bacteria/aquifex/aquifex.ht
m
also the oldest Banded Iron Formation,
on Akilia Island in Western Greenland.
The oldest evidence for life on earth
was found in this rock by measuring the
ratio of carbon 12 to carbon 13 in
grains of apatite (calcium phosphate)
from this rock. Life uses the lighter
Carbon-12 isotope and not Carbon-13 and
so the ratio of carbon-12 to carbon-13
is different from a nonliving source
(calcium carbonate or limestone).
source: nature 11/7/96
Banded Iron Formation Rocks. These
rocks are sedimentary. They are made
of iron rich chert (silicates, like
SiO2). These rocks have alternative
bands of orange or yellow and black.
In the red parts the iron is oxydized
(contains iron oxides, either hematite
{Fe2O3 = rust} or magnetite {Fe3O4]}).
These bands may have formed because
photosynthetic bacteria (in
stromatolites found in shallow ocean
shores, and purple bacteria floating in
water) produce oxygen from CO2 during
photosynthesis. When the level of
oxygen in the water became too high,
many bacteria died, and this cycle
created the BIF. But BIF also may form
naturally when photons in uv
frequencies split H2O into H2 and O2.
So perhaps the BIF bands represent
cycles of more or less uv light
reaching the earth. Perhaps the
alternating phenomenon is similar to
eukaryotic algal blooms. In any event,
this free oxygen bonded with the many
tons of iron dissolved in the water to
form insoluable iron oxide which then
fell to the ocean floor to form the
orange layers of Banded Iron Formation.
How these alternating bands are made
is not clear and has not yet been
duplicated in a lab.
This cycle of alternating orange and
black bands will continue for 2 billion
years until 1,800 million years before
now. This is the beginning of oxygen
production on earth, the atmosphere of
earth still has only small amounts of
oxygen at this time.
It is amazing that
people are still not certain what was
the cause of the oxygen, and the cycles
that deposited the banded Iron
Formation.
source: nature 11/7/96
formation, SW Greenland.
[1] Fig. 5. (a) Carbonaceous
microstructure from Isua Banded iron
formation, SW-Greenland (ca 3.85 Ga).
(b) Laser mass spectrum (negative ions)
from similar specimen. Field of
measurement ca 1 small mu, Greekm
diameter.
source: http://www.sciencedirect.com/sci
ence?_ob=MiamiCaptionURL&_method=retriev
e&_udi=B6VBP-42G6M5T-7&_image=fig7&_ba=7
&_user=4422&_coverDate=02%2F01%2F2001&_f
mt=full&_orig=browse&_cdi=5932&view=c&_a
cct=C000059600&_version=1&_urlVersion=0&
_userid=4422&md5=fe1052cbc18dba545ec95c2
e7ff3090b
Greenland Banded Iron Formation
sediment are evidence of the existence
of Archaea.
and Hydrocarbon molecules (alkanes)
detected in 3760 billion year old Isua
Banded Iron Formation, indicate the
possibility of photosynthetic sulfate
reducing bacteria (Archaea, for example
Sulpholobus) and Cyanobacteria living
at that time.
in Isua, Greenland Banded Iron
Formation evidence of prokaryote Oxygen
photosynthesis.
sediment in Australia shown to be
consistent with planktonic
photosynthesizing organisms.
[1] Figure 1. (A) Turbidite sedimentary
rocks from the Isua supracrustal belt,
west Greenland. The notebook is 17 cm
wide. (B) A close-up of finely
laminated slate representing pelagic
mud. The hammer is 70 cm long. (C)
Photomicrograph of sample 810213,
showing finely laminated pelagic mud.
The variation in color is mainly due to
variations in C abundance. (D)
Photomicrograph of C grains arranged
along a buckled stringer. (E)
Backscattered electron image of a
polished surface (sample 810213),
showing the distribution of C grains as
black areas. (F) Backscattered electron
image of a polished surface (sample
810213), showing the rounded shape of C
grains (black).
source: http://www.sciencemag.org/cgi/co
ntent/full/283/5402/674
Archaebacteria (Archaea) Phylum,
Korarchaeotes evolving now.
[1] DNA tree
source: http://www.uni-giessen.de/~gf126
5/GROUPS/KLUG/Stammbaum.html
[2] Scanning electron micrograph of
the Obsidian Pool enrichment culture.
Barns et al. discovered the
Korarchaeota lineage in Obsidian Pool
over a decade ago, using what were
highly innovative methods for the time.
Since their discovery, the Korarchaeota
group of microorganisms still remains
mostly uncharacterized. The group is
primarily defined only by 16S ribosomal
RNA sequences obtained from a variety
of marine and terrestrial hydrothermal
environments. The 16S-rRNA-based
phylogeny of the Korarchaeota suggests
that this group forms a very deep,
kingdom-level, major lineage within the
archaeal domain. PD
source: http://www.jgi.doe.gov/sequencin
g/why/CSP2006/korarchaeota.jpg
yet found. Stromatolites made by
photosynthetic bacteria found in both
Warrawoona, Western Australia, and Fig
Tree Group, South Africa.
[1] image on left is from swaziland
source: nature feb 6
source: 1986
thought to be cyanobacteria, found in
3,500 Million Year old chert from South
Africa and 3,465 Million year old Apex
chert of north-western Australia.
Oldest fossils
of an organism, thought to be
cyanobacteria, found in 3,500 Million
Year old chert from South Africa and
3,465 Million year old Apex chert of
the Pilbara Supergroup, Warrawoona
Group, northwestern Western Australia.
Some people argue that these are not
fossils of bacteria but abiotic
material. Most genetic timelines put
the origin of cyanobacteria much later
around 2,700mybn.
Cyanobacteria evolved
multicellularity where cellular
differentiation occurs.
[1] Figure 1 Optical photomicrographs
showing carbonaceous (kerogenous)
filamentous microbial fossils in
petrographic thin sections of
Precambrian cherts. Scale in a
represents images in a and c-i; scale
in b represents image in b. All parts
show photomontages, which is
necessitated by the three-dimensional
preservation of the cylindrical sinuous
permineralized microbes. Squares in
each part indicate the areas for which
chemical data are presented in Figs 2
and 3. a, An unnamed cylindrical
prokaryotic filament, probably the
degraded cellular trichome or tubular
sheath of an oscillatoriacean
cyanobacterium, from the 770-Myr
Skillogalee Dolomite of South
Australia12. b, Gunflintia grandis, a
cellular probably oscillatoriacean
trichome, from the 2,100-Myr Gunflint
Formation of Ontario, Canada13. c, d,
Unnamed highly carbonized filamentous
prokaryotes from the 3,375-Myr Kromberg
Formation of South Africa14: the poorly
preserved cylindrical trichome of a
noncyanobacterial or oscillatoriacean
prokaryote (c); the disrupted,
originally cellular trichomic remnants
possibly of an Oscillatoria- or
Lyngbya-like cyanobacterium (d). e-i,
Cellular microbial filaments from the
3,465-Myr Apex chert of northwestern
Western Australia: Primaevifilum
amoenum4,5, from the collections of The
Natural History Museum (TNHM), London,
specimen V.63164[6] (e); P. amoenum4
(f); the holotype of P.
delicatulum4,5,15, TNHM V.63165[2] (g);
P. conicoterminatum5, TNHM V63164[9]
(h); the holotype of Eoleptonema apex5,
TNHM V.63729[1] (i).
source: Nature416
[2] Fig. 3 Filamentous microfossils:
a, cylindrical microfossil from
Hooggenoeg sample; b, threadlike and
tubular filaments extending between
laminae, Kromberg sample; c,d,e,
tubular filamnets oriented subparallel
to bedding, Kromberg sample; f,
threadlike filament flattened parallel
to bedding, Kromberg sample.
source: 73 - 76 (07 Mar 2002) Letters
to Nature
http://www.nature.com/nature/journal/v41
6/n6876/fig_tab/416073a_F1.html
eukaryotes happened here at 3.5 bybn.
evidence of moderate thermophile
sulphur reducing prokaryotes from North
Pole, Australia.
[1] get larger image
source: file:///root/web/fossils_biomark
er_science_v67_i22_nov_15_2003.html#bib9
9
bacteria.
[1] The tree is modified from ref. 2,
and abstracted from phylogenetic trees
presented in refs 26 and 27. The time
calibration points are from ref. 30,
with our additional constraint of 3.47
Gyr placed in the Bacterial domain.
Lineages housing sulphate-reducers
metabolizing at temperatures > 70 °C
are shown by broken black lines, while
lineages supporting sulphate-reducers
metabolizing at < 70 °C are shown by heavy black lines.
source: http://www.nature.com/nature/jou
rnal/v410/n6824/fig_tab/410077a0_F4.html
photosynthetic bacteria found in
Pilbara Craton, Australia.
[1] a-c, 'Encrusting/domical
laminites'; d-f, 'small crested/conical
laminites'; g-i, 'cuspate swales'; j-l,
'large complex cones' (dashed lines in
k trace lamina shape and show outlines
of intraclast conglomerate piled
against the cone at two levels). m-o,
'Egg-carton laminites'; p, q, 'wavy
laminites'; r-t, 'iron-rich laminites'
(t is a cut slab). The scale card in b,
h and i is 18 cm. The scale card
increments in c, e, k, l, n and s are 1
cm. The scale bar in o is about 1 cm.
The scale bars in the remaining
pictures are about 5 cm. COPYRIGHTED
source: http://www.nature.com/nature/jou
rnal/v441/n7094/fig_tab/nature04764_F1.h
tml
photosynthetic, probably anoxygenic,
bacteria that lived in mats in the
ocean date to this time.
[1] a, Dark carbonaceous laminations
draping an underlying coarse detrital
carbonaceous grain (a), showing
internal anastomosing and draping
character (b) and, at the top (c)
draping irregularities in underlying
carbonaceous laminations. b, Dark
carbonaceous laminations that have been
eroded and rolled up by currents. c,
Bundled filaments in the rolled
laminations in b [tp: they should
have clearly indicated that they are
saying that these filaments are
bacteria].
source: http://www.nature.com/nature/jou
rnal/v431/n7008/fig_tab/nature02888_F4.h
tml
Swaziland System, South Africa.
[1] Fig. 3. (a,b) Organic
microstructures from Kromberg
Formation, Swaziland System, South
Africa (ca 3.4 Ga). TEM-micrographs of
demineralized specimens. (c) Portion of
organic microstructure from Bulawaya
stromatolite (see Fig. 2). (d) Portion
of the mucilagenous sheath of recent
Anabaena sp., cyanobacteria (Fig. d
after Leak, 1967). For magnification of
Fig. c see scale of Fig. a.
source: http://www.sciencedirect.com/sci
ence?_ob=MiamiCaptionURL&_method=retriev
e&_udi=B6VBP-42G6M5T-7&_image=fig9&_ba=9
&_user=4422&_coverDate=02%2F01%2F2001&_f
mt=full&_orig=browse&_cdi=5932&view=c&_a
cct=C000059600&_version=1&_urlVersion=0&
_userid=4422&md5=27a45a0804747bb4b74eaac
305df2905
Different from binary division, where a
cell is split in half, in budding, a
new complete cell is made in the
original cell, and the new cell bursts
through the cell wall, the original
cell wall must then be repaired.
Budding is the
only other method of reproduction known
in prokaryotes besides binary fission.
The only major difference between
prokaryote budding and binary division
are that one or more new cells are
completely formed inside the original
cell, where in binary division part of
the original cell wall is used to make
the new cell.
In budding, a complete new cell is
synthesized from a DNA template, where
in binary division only the DNA is
duplicated and more cytoplasm and cell
wall is synthesized. So, budding
preserves organelles made by the main
DNA template that cannot duplicate
themselves and would not get duplicated
or synthesized in binary division, for
example, flagella.
Although it is very unlikely,
the possibility does exist that
prokaryote budding evolved from a
eukaryote that lost it's nucleus.
[1] Evolutionary relationships of model
organisms and bacteria that show
unusual reproductive strategies. This
phylogenetic tree (a) illustrates the
diversity of organisms that use the
alternative reproductive strategies
shown in (b). Bold type indicates
complete or ongoing genome projects.
Intracellular offspring are produced by
several low-GC Gram-positive bacteria
such as Metabacterium polyspora,
Epulopiscium spp. and the segmented
filamentous bacteria (SFB). Budding and
multiple fission are found in the
proteobacterial genera Hyphomonas and
Bdellovibrio, respectively. In the case
of the Cyanobacteria, Stanieria
produces baeocytes and Chamaesiphon
produces offspring by budding.
Actinoplanes produce dispersible
offspring by multiple fission of
filaments within the sporangium.
source: http://www.nature.com/nrmicro/jo
urnal/v3/n3/full/nrmicro1096_fs.html
(Nature Reviews Microbiology 3
[2] Electron micrograph of a
Pirellula bacterium from giant tiger
prawn tissue (Penaeus monodon). Notice
the large crateriform structures (C) on
the cell surface and flagella. From
Fuerst et al.
source: 214-224 (2005);
doi:10.1038/nrmicro1096)
South Africa are oldest evidence of
procaryotes that reproduce by budding
and not binary fission.
[1] Fig. 4. (a-d) Organic
microstructures from Swartkoppie chert,
South Africa (ca 3.25 Ga).
TEM-micrographs of demineralized
specimen (a,b) Laser mass spectra
(negative ions) from clusters of
similar specimens. Field of measurement
ca 1 small mu, Greekm diameter. (c,d)
TEM-micrographs from demineralized Thin
section. (e) Recent budding iron
bacterium Pedomicrobium sp. (Fig. e
from Ghiorse and Hirsch, 1979).
source: http://www.sciencedirect.com/sci
ence?_ob=MiamiCaptionURL&_method=retriev
e&_udi=B6VBP-42G6M5T-7&_image=fig6&_ba=6
&_user=4422&_coverDate=02%2F01%2F2001&_f
mt=full&_orig=browse&_cdi=5932&view=c&_a
cct=C000059600&_version=1&_urlVersion=0&
_userid=4422&md5=801178ddb930bd041063bae
7a3e0e204
found in 3235 million year old deep-sea
volcanogenic massive sulphide deposits
from the Pilbara Craton of Australia
may be oldest Archaea fossils.
[1] Photomicrographs of filaments from
the Sulphur Springs VMS deposit. Scale
bar, 10 µm. a-f, Straight, sinuous and
curved morphologies, some densely
intertwined. g, Filaments parallel to
the concentric layering. h, Filaments
oriented sub-perpendicular to
banding.
source:
G+C {Guanine and Cytosine count} Gram
positive) evolve.
Genetic comparison shows
Eubacteria Phylum Firmicutes (low G+C
{Guanine and Cytosine count} Gram
positive) evolving here.
Firmicutes include the Classes:
Bacillus (anthrax), Listeria,
Mollicutes, and Stephylococcus.
Firmicutes may be the
first rod shaped bacteria, and first
bacteria to have a gram positive cell
wall.
The peptidoglycan layer is thicker in
Gram-positive bacteria (20 to 80 nm)
than in Gram-negative bacteria (7 to 8
nm)
Firmicultes form endospores, and is the
only phlyum of bacteria that evolved
the ability to build endospores.
The Firmicutes
are a division of bacteria, most of
which have Gram-positive stains. A few,
the Mollicutes or mycoplasmas, lack
cell walls altogether and so do not
respond to Gram staining, but still
lack the second membrane found in other
Gram-negative forms. Originally the
Firmicutes were taken to include all
Gram-positive bacteria, but more
recently they tend to be restricted to
a core group of related forms, called
the low G+C group in contrast to the
Actinobacteria. They have round cells,
called cocci (singular coccus), or
rod-shaped forms.
Many Firmicutes produce endospores,
which are resistant to desiccation and
can survive extreme conditions. They
are found in various environments, and
some notable pathogens. Those in one
family, the heliobacteria, produce
energy through photosynthesis.
Firmicutes include:
CLASS Bacilli (rod shaped)
ORDER
Bacillales (anthrax)
ORDER Lactobacillales
CLASS Clostridia
ORDER
Clostridiales
ORDER Halanaerobiales
ORDER
Thermoanaerobacteriales
CLASS Mollicutes
ORDER Mycoplasmatales
ORDER
Entomoplasmatales
ORDER Anaeroplasmatales
ORDER Acholeplasmatales
[1] Listeria monocytogenes is a
Gram-positive bacterium, in the
division Firmicutes, named for Joseph
Lister. It is motile by means of
flagella. Some studies suggest that 1
to 10% of humans may carry L.
monocytogenes in their
intestines. Researchers have found L.
monocytogenes in at least 37 mammalian
species, both domesticated and feral,
as well as in at least 17 species of
birds and possibly in some species of
fish and shellfish. Laboratories can
isolate L. monocytogenes from soil,
silage, and other environmental
sources. L. monocytogenes is quite
hardy and resists the deleterious
effects of freezing, drying, and heat
remarkably well for a bacterium that
does not form spores. Most L.
monocytogenes are pathogenic to some
degree.
source: http://en.wikipedia.org/wiki/Ima
ge:Listeria.jpg
[2] These are bacteria (about 0.3 µm
in diameter) that do not have outer
walls, only cytoplasmic membranes.
However, they do have cytoskeletal
elements that give them a distinct
non-spherical shape. They look like
schmoos that are pulled along by their
heads. How they are able to glide is a
mystery.
source: http://webmac.rowland.org/labs/b
acteria/projects_glide.html
abililty to form endpospores.
An endospore is any
spore that is produced within an
organism (usually a bacterium). Most
bacterium produce only one spore, as
this is not a reproduction process.
This is in contrast to exospores, which
are rather produced by growth or
budding. The primary function of most
endospores is to ensure the survival of
a colony through periods of
environmental stress. Endospores are
therefore resistant to desiccation,
temperature, starvation, ultraviolet
and gamma radiation, and chemical
disinfectants.
One of the great questions of this time
is: "what is the process behind cell
differentiation and cell growth?" How
is each stage initiated and stopped?
There are a number of theories. One
theory presumes the entire DNA strand
is accessible at all times. In this
view operons are used sequentially,
while many proteins are supressed, some
operons are active, which results in
one set of proteins developing the
cell, at some point, the first group of
operons are inhibited and a different
operon (or set of operons) is turned
on, signalling a new set of proteins to
be built which effects the growth and
shape of the cell. An abundance of a
first stage protein might initiate the
second stage. A second theory is that
DNA is read like a computer program
with some proteins moving along the DNA
strand, one part at a time. In this
way, one portion of the DNA may reflect
one life stage, while the next portion
represents the next (and perhaps very
different) life stage.
The endospore-forming bacteria belong
to the Firmicutes.
[1] Spore forming inside a bacterium.
Stahly, MicrobeLibrary COPYRIGHTED
source: http://www.microbe.org/microbes/
spores.asp
ancestor of all Proteobacteria
(Rickettsia {mitochondria}, gonorrhoea,
Salmonella, E coli) evolving now.
Proteobact
eria include 5 Classes:
CLASS Alpha
Proteobacteria (Rickettsia Prowazekii
{mitochondria/typhus})
CLASS Beta Proteobacteria (Neisseria
gonorrhoeae {gonorrhoea})
CLASS Gamma Proteobacteria
(Salmonella and Escherichia coli.)
CLASS Delta
Proteobacteria
CLASS Epsilon Proteobacteria
The Proteobacteria are a major group of
bacteria. They include a wide variety
of pathogens, such as Escherichia,
Salmonella, Vibrio, Helicobacter, and
many other notable genera. Others are
free-living, and include many of the
bacteria responsible for nitrogen
fixation. The group is defined
primarily in terms of ribosomal RNA
(rRNA) sequences, and is named for the
Greek god Proteus, who could change his
shape, because of the great diversity
of forms found in it.
All Proteobacteria are Gram-negative,
with an outer membrane mainly composed
of lipopolysaccharides. Many move about
using flagella, but some are non-motile
or rely on bacterial gliding. The last
include the myxobacteria, a unique
group of bacteria that can aggregate to
form multicellular fruiting bodies.
There is also a wide variety in the
types of metabolism. Most members are
facultatively or obligately anaerobic
and heterotrophic, but there are
numerous exceptions. A variety of
genera, which are not closely related,
can photosynthesize. These are called
purple bacteria, referring to their
mostly reddish pigmentation.
The delta-proteobacteria Myxobacteria
is capable of colonial multicellularity
and some view as possibly being the
bacteria that formed the cytoplasm in
eukaryotes.
CLASS Alpha Proteobacteria (Rickettsia
Prowazekii {mitochondria/typhus})
CLASS Beta Proteobacteria
(Neisseria gonorrhoeae {gonorrhoea})
CLASS Gamma
Proteobacteria (Salmonella, Escherichia
coli., fireblight {Erwinia amylovora},
one form of dysentery {Shigella
dysenteriae}, Legionaires' disease
{Legionella pneumophilia}, Haemophilus
influenzae {first free living organism
to have entire genome sequenced},
Pseudomonas, the largest known bacteria
{Thiomargarita namibiensis}, Cholera
{Vibrio cholerae})
The number of individual E.
coli bacteria in the feces that one
human passes in one day averages
between 100 billion and 10 trillion.
CLA
SS Delta Proteobacteria (Bdellovibrio
{parasite on other bacteria}, Geobacter
{can oxydize uranium, may be used as
battery that runs on waste},
myxobacteria {form multicellular bodies
that make spores, have large genome}
CLASS
Epsilon Proteobacteria (Helicobacter
{spiral bacteria})
[1] Figure 1. Transmission electron
micrograph of the ELB agent in XTC-2
cells. The rickettsia are free in the
cytoplasm and surrounded by an electron
transparent halo. Original
magnification X 30,000. CDC PD
source: www.cdc.gov/ncidod/
eid/vol7no1/raoultG1.htm
[2] Caulobacter crescentus. From
http://sunflower.bio.indiana.edu/~ybrun/
L305.html COPYRIGHTED EDU was in wiki
but appears to be removed
source: http://upload.wikimedia.org/wiki
pedia/en/4/42/Caulobacter.jpg
Eubacteria Phylum, Planctomycetes
(Planctobacteria) evolving now.
Planctomycet
es are a possible ancestor of all
eukaryotes because the circle of DNA
can sometimes be enclosed in a double
membrane.
Planctomycetes is a small phylum with
only 4 Genera, require oxygen for
growth (obligately aerobic), are found
in fresh and salt water. They reproduce
by budding. They have holdfast (stalk)
at the nonreproductive end that helps
them to attach to each other during
budding.
The life cycle involves alternation
between sessile cells and flagellated
swarmer cells. The sessile cells bud to
form the flagellated swarmer cells
which swim for a while before settling
down to attach and begin reproduction.
It is also possible, although unlikely,
that planctomycetes are descended from
a very early eukaryote that lost the
nucleus but retained the cytoplasmic
DNA, since budding may have evolved as
a method to duplicate a eukaryote cell
from the nucleus. (ok this is out
there...maybe t3)
The organisms belonging
to this group lack murein in their cell
wall Murein is an important
heteropolymer present in most bacterial
cell walls that serves as a protective
component in the cell wall skeleton.
Instead their walls are made up of
glycoprotein rich in glutamate.
Planctomycetes have internal structures
that are more complex than would be
typically expected in prokaryotes.
While they don't have a nucleus in the
eukaryotic sense, the nuclear material
can sometimes be enclosed in a double
membrane. In addition to this nucleoid,
there are two other membrane-separated
compartments; the pirrellulosome or
riboplasm, which contains the ribosome
and related proteins, and the
ribosome-free paryphoplasm.
[1] Electron micrographs of cells of
new Gemmata-like and Isosphaera-like
isolates. (A) Negatively stained cell
of the Gemmata-like strain JW11-2f5
showing crateriform structures
(arrowhead) and coccoid cell
morphology. Bar marker, 200 nm. (B)
Negatively stained budding cell of
Isosphaera-like strain CJuql1 showing
uniform crateriform structures
(arrowhead) on the mother cell and
coccoid cell morphology. Bar marker,
200 nm. (C) Thin section of
Gemmata-like cryosubstituted cell of
strain JW3-8s0 showing the
double-membrane-bounded nuclear body
(NB) and nucleoid (N) enclosed within
it. Bar marker, 200 nm. (D) Thin
section of Isosphaera-like strain C2-3
possessing a fibrillar nucleoid (N)
within a cytoplasmic compartment
bounded by a single membrane (M) only.
Bar marker, 200 nm. Appl Environ
Microbiol. 2002 January; 68(1):
417-422. doi:
10.1128/AEM.68.1.417-422.2002.
source: http://www.pubmedcentral.gov/art
iclerender.fcgi?tool=pubmed&pubmedid=117
72655
[2] Evolutionary distance tree
derived from comparative analysis of
16S rDNAs from freshwater and soil
isolates and reference strains of the
order Planctomycetales. Database
accession numbers are shown in
parentheses after species, strain, or
clone names. Bootstrap values of
greater than 70% from 100 bootstrap
resamplings from the distance analysis
are presented at nodes. Thermotoga
maritima was used as an outgroup.
Isolates from this study and
representative named species of the
planctomycetes are indicated in bold.
The scale bar represents 0.1 nucleotide
substitution per nucleotide
position. Appl Environ Microbiol.
2002 January; 68(1): 417-422. doi:
10.1128/AEM.68.1.417-422.2002.
source: http://florey.biosci.uq.edu.au/m
ypa/images/fuerst2.gif
Eubacteria Phylum, Actinobacteria (high
G+C, Gram positive) evolving now.
Actinobact
eria have 5 Orders:
ORDER Acidimicrobiales
ORDER
Actinobacteriales
ORDER Coriobacteriales
ORDER Rubrobacteriales
ORDER Sphaerobacteriales
Actinobacteria include the causes of
tuberculosis (Mycobacteria
tuberculosis) and leprosy (Mycobacteria
leprae).
The Actinobacteria or Actinomycetes are
a group of Gram-positive bacteria. Most
are found in the soil, and they include
some of the most common soil life,
playing an important role in
decomposition of organic materials,
such as cellulose and chitin. This
replenishes the supply of nutrients in
the soil and is an important part of
humus formation. Other Actinobacteria
inhabit plants and animals, including a
few pathogens, such as Mycobacterium.
Some
Actinobacteria form braching filaments,
which somewhat resemble the mycelia of
the unrelated fungi, among which they
were originally classified under the
older name Actinomycetes. Most members
are aerobic, but a few, such as
Actinomyces israelii, can grow under
anaerobic conditions. Unlike the
Firmicutes, the other main group of
Gram-positive bacteria, they have DNA
with a high GC-content
{guanine-cytosine content} and some
Actinomycetes species produce external
spores.
Mycobacterium bovis (the bacterium
responsible for bovine TB) in
particular has been estimated to be
responsible, for the period of the
first half of the 20th century, for
more losses among farm animals than all
other infectious diseases combined.
Infection occurs if the bacterium is
ingested.
Actinobacteria are unsurpassed in their
ability to produce many compounds that
have pharmaceutically useful
properties. In 1940 Selman Waksman
discovered that the soil bacteria he
was studying made actinomycin, a
discovery which granted him a Nobel
Prize. Since then hundreds of naturally
occurring antibiotics have been
discovered in these terrestrial
microorganisms, especially from the
genus Streptomyces.
When M.leprae was discovered by G.A.
Hansen in 1873, it was the first
bacterium to be identified as causing
disease in man. Although Leprosy is
contagious, it is not widespread
because 95% of the population have
immune systems able to cope with the
bacteria.
[1] Frankia is a genus of
nitrogen-fixing soil bacteria, which
possesses a set of features that are
unique amongst symbiotic
nitrogen-fixing microorganisms,
including rhizobia, making it an
attractive taxon to study. These
heterotrophic Gram-positive bacteria
which are able to induce symbiotic
nitrogen-fixing root nodules
(actinorhizas) in a wide range of
dicotyledonous species (actinorhizal
plants), have also the capacity to fix
atmospheric nitrogen in culture and
under aerobic conditions.
source: http://www.ibmc.up.pt/webpagesgr
upos/cam/Frankia.htm
[2] Aerial mycelium and spore of
Streptomyces coelicolor. The mycelium
and the oval spores are about 1µm
wide, typical for bacteria and much
smaller than fungal hyphae and spores.
(Scanning electron micrograph, Mark
Buttner, Kim Findlay, John Innes
Centre). COPYRIGHT UK
source: http://www.sanger.ac.uk/Projects
/S_coelicolor/micro_image4.shtml
Eubacteria Phylum, Spirochaetes
(Syphilis, Lyme disease) evolving now.
Inclu
des leptospirosis (leptospira), Lyme
disease (Borrelia burgdorferi), and
Syphilis (Treponema pallidum).
Spirochaetes only
have one order:
ORDER Spirochaetales
This is when the first spiral shaped
bacteria evolve.
The spirochaetes (or spirochetes) are a
phylum of distinctive bacteria, which
have long, helically coiled cells. They
are distinguished by the presence of
flagella running lengthwise between the
cell membrane and cell wall, called
axial filaments. These cause a twisting
motion which allows the spirochaete to
move about. Most spirochaetes are
free-living and anaerobic, but there
are numerous exceptions.
Spirochaetes only have
one order:
ORDER Spirochaetales
and 3 families.
[1] Syphilis is a complex, sexually
transmitted disease (STD) with a highly
variable clinical course. The disease
is caused by the bacterium, Treponema
pallidum. In the United States, 32,871
cases of syphilis, including 432 cases
of congenital syphilis, were detected
by public health officials in 2002.
Eight of the ten states with the
highest rates of syphilis are located
in the southern region of the United
States.
source: http://www.cdc.gov/nchstp/od/tus
kegee/syphilis.htm
[2] leptospirose 200x magnified with
dark-field microscope photo taken by
bluuurgh at the dutch royal tropical
institute (www.kit.nl) PD
source: http://uhavax.hartford.edu/bugl/
images/Treponema%20pallidum.jpg
Eubacteria Phyla Bacteroidetes and
Chlorobi (green sulphur bacteria)
evolving now.
PHYLUM Bacteroidetes
CLASS Bacteroides
ORDER
Bacteroidales
CLASS Flavobacteria
ORDER Flavobacteriales
CLASS
Sphingobacteria
ORDER Sphingobacteriales
PHLYUM Chlorobi (Green sulphur)
CLASS Chlorobia
ORDER
Chlorobiales
The phylum Bacteroidetes is composed of
three large groups of bacteria. By far,
more is written about and known about
the Bacteroides class, than the other
two, the Flavobacteria and the
Sphingobacteria classes. They are
related by the similarity in the
composition of the small 16S subunit of
their ribosomes. Members of the
bacteroides class are human commensals
(they benefit but humans receive no
effect) and sometimes pathogens.
Members of the other two classes are
rarely pathogenic to humans.
Chlorobi are the "green sulphur
bacteria", are a family of phototrophic
(photosynthesizing) bacteria. Green
sulfur bacteria are generally nonmotile
(one species has a flagellum), and come
in spheres, rods, and spirals. Their
environment must be oxygen-free, and
they need light to grow. They engage in
photosynthesis, using
bacteriochlorophylls c, d, and e in
vesicles called chlorosomes attached to
the membrane. They use sulfide ions as
electron donor, and in the process the
sulfide gets oxidized, producing
globules of elemental sulfur outside
the cell, which may then be further
oxidized. (By contrast, the
photosynthesis in plants uses water as
electron donor and produces oxygen.)
A species of green sulfur bacteria has
been found living near a black smoker
off the coast of Mexico at a depth of
2,500 meters beneath the surface of the
Pacific Ocean. At this depth, the
bacteria, designated GSB1, lives off
the dim glow of the thermal vent since
no sunlight can penetrate to that
depth.
[1] Bacteroides fragilis . From the
Zdravotni University
source: http://biology.kenyon.edu/Microb
ial_Biorealm/bacteria/bacteroidete_chlor
ob_group/bacteroides/bacteroides.htm
[2] Cross section of a Bacteroides
showing an outer membrane, a
peptidoglycan layer, and a cytoplasmic
membrane. From New-asthma
source: http://phil.cdc.gov/phil/details
.asp
Eubacteria Phyla Chlamydiae and
Verrucomicrobia evolving now.
Chlamydiae
includes (clamydia, trachoma {Chlamydia
trachomatis}, a form of pneumonia
{Chlamydophila pneumoniae}, psittacosis
{Chlamydophila psittaci}.
CLASS Chlamydiae
ORDER Chlamydiales
PHYLA Verrucomicrobia
ORDER Verrucomicrobiales
The Chlamydiae are a group of bacteria,
all of which are intracellular
parasites of eukaryotic cells. Most
described species infect mammals and
birds, but some have been found in
other hosts, such as amoebae.
Chlamydiae have a
life-cycle involving two distinct
forms. Infection takes place by means
of elementary bodies (EB), which are
metabolically inactive. These are taken
up within a cellular vacuole, where
they grow into larger reticulate bodies
(RB), which reproduce. Ultimately new
elementary bodies are produced and
expelled from the cell.
Verrucomicrobia is a recently described
phylum of bacteria. This phylum
contains only a few described species
(Verrucomicrobia spinosum, is an
example, the phylum is named after
this). The species identified have been
isolated from fresh water and soil
environments and human feces. A number
of as-yet uncultivated species have
been identified in association with
eukaryotic hosts including extrusive
explosive ectosymbionts of protists and
endosymbionts of nematodes residing in
their gametes.
Evidence suggests that verrucomicrobia
are abundant within the environment,
and important (especially to soil
cultures). This phylum is considered to
have two sister phyla Chlamydiae and
Lentisphaera.
There are three main species of
chlamydiae that infect humans:
* Chlamydia trachomatis, which
causes the eye-disease trachoma and the
sexually transmitted infection
chlamydia;
* Chlamydophila pneumoniae, which
causes a form of pneumonia;
* Chlamydophila
psittaci, which causes psittacosis.
[1] Chlamydia trachomatis wiki, is
copyrighted
source: http://en.wikipedia.org/wiki/Chl
amydia_trachomatis
[2] wiki, public domain
source: http://en.wikipedia.org/wiki/Ima
ge:Chlamydophila_pneumoniae.jpg
cell membrane folds around some
molecules to form a spherical vesicle
which enters the cytoplasm, and
exocytosis, the opposite process, where
a vesicle combines with a call membrane
to empty molecules outside a cell both
evolve in an early eukaryote cell.
Eukaryote cells can now swallow
bacteria (phagocytosis) and liquid
(pinocytosis). The cells can then
(heterotrophically) use the molecules
injested (for example a bacterium) for
copying and to make ATP. This is the
first time one cell can eat a different
living cell.
How similar endocytosis is to
conjugation is unknown at this time.
[1] Pinocytosis In the process of
pinocytosis the plasma membrane froms
an invagination. What ever substance
is found within the area of
invagination is brought into the
cell. In general this material will
be dissolved in water and thus this
process is also refered to as
''cellular drinking'' to indicate that
liquids and material dissolved in
liquids are ingested by the
cell. This is opposed to the
ingestion of large particulate material
like bacteria or other cells or cell
debris.
source: http://academic.brooklyn.cuny.ed
u/biology/bio4fv/page/endocytb.htm
cytoplasm.
One theory is that the cytoskeleton
formed from the eukaryote flagella
(cilia, undulipodia) tubules.
Cytoskeleton is a
single body with the endoplasmic
reticulum and nuclear membrane?
This cell has a nucleus, with either
single strands or a circle of DNA
inside. This is a single anaerobic
cell. This is the first protist.
This cell evolves either by:
1) two or more
bacteria joined, one with flagella
(perhaps a eubacteria) formed the
nucleus, a second formed the cytoplasm
outside the nucleus, eventually the
code to build the entire cell including
the instructions to build the symbiotic
captured bacteria was included in the
new nucleus,
2) the nucleus formed as
part of the cytoplasm lattice, perhaps
the outer wall folded in on itself
creating a double membrane, or a
membrane grew around the DNA (for
example like planctobacteria) which
provided more protection for the DNA
from the movement and digestive
activities of cytoplasm now without a
rigid cell wall,
3) a bacteria with
flagella that grew cytoplasm and a
secondary cell wall outside the
original cell wall,
4) a virus,
5) a
DNA strand from conjugation with a
different prokaryote stored in a
vesicle.
There are key features that are
different from eukaryotes and
prokaryotes:
1) Eukaryotes have a nucleus,
prokaryotes do not.
2) DNA in eukaryotes is
in the form of chromosomes, in
prokaryotes the DNA is in a circle.
3)
Eukaryotes can do endocytosis, fold
their cell membrane around some
external object and injest the object,
prokaryotes can not.
4) Eukaryotes have a
membrane lattice of proteins, actin and
myacin, prokaryotes do not.
5) Eukaryotes
have an endoplasmic reticulum and golgi
body.
6) Eukaryotes reproduce asexually by
dual binary division (both nucleus and
cell divide by binary division),
budding, or mitosis, prokaryotes
reproduce by budding or binary
division.
If the nucleus is an engulfed
prokaryote, this cell inherits the
processes of nuclear DNA duplication
and nucleus division (karyokinesis)
from prokaryote binary division.
Initially, both the nucleus and cell
divide by binary division.
Support for the
nucleus forming from a prokaryote is
that chromosomes in parabasalia and
dinoflagellates remain permanently
anchored to the nuclear membrane
(envelope?) by the kinetochores, the
same way prokaryote DNA anchors to the
cell membrane (wall?) during cell
division.
A theory of an archaebacteria (perhaps
an eocyte) forming the first eukaryote
nucleus and a gram-negative eubacteria
forming the cytoplasm of the first
eukaryote is supported by genetic
evidence.
This cell reproduces asexually by
either binary fission (both nucleus and
cytoplasm) or budding, or sexually by
conjugation or both cell and nuclei
fully merging.
If this cell has chromosomes, this is
the first (haploid) organism with
chromosomes.
Perhaps a sperm-like flagellated
prokaryote merged with an ovum-like
prokaryote from the same or a different
species, perhaps by the ovum opening a
pilus and the sperm-like cell entering
the pilus, and once inside opening a
pilus through which the DNA from the
two cells could merge. Many
diplomonads look like sperm cells stuck
in an ovum, with the still flagellated
sperm forming the nucleus, and some
diplomonads, for example, the oxymonad,
Saccinobaculus reproduce sexually.
An important evolutionary step had to
evolve here, and that is the evolution
of the prokaryote binary division
system: 1) duplicating DNA in the
cytoplasm, 2) separating the two copies
of DNA, and 3) the division of
cytoplasm into two cells to an adapted
process of eukaryote cell division: 1)
duplicating DNA in the nucleus, 2)
separating the DNA in the nucleus, 3)
dividing the nucleus into two nuclei,
4) separating the two nuclei, and then
5) dividing the cytoplasm into two
cells.
It appears in early eukaryote nuclei
(as seen in closed mitosis, where the
nuclear membrane persistes through
mitosis) that the nuclei divide by a
process similar to binary division (as
opposed to budding), which adds to the
support for the first nucleus being a
prokaryote and continuing to divide by
binary division.
Most people accept that the centrioles
from which grow the microtubule
spindles that pull apart chromosomes in
mitosis, evolved from the base pairs
which originally were, and on some
species still are, connected to a
cilium.
Perhaps there are some eukaryote nuclei
that duplicate by budding, although
this has never been found to my
knowledge. If ever found, that would
imply that budding evolved before the
first eukaryote, but could have
possibly evolved after by simply
dropping the instructions to copy
anything other than the nucleus.
Binary cell division in the most basic
form only synthesizes more cytoplasm
and cell wall, where budding reproduces
the entire body plan of a cell (or
nucleus in this case).
evidence for
prokaryote=eukaryote nucleus
1) flagella
connected to nucleus of metamonads.
a) flagella
hints that nucleus prokaryote may have
been a male gamete (and the cytoplasm
the female gamete).
b) flagella are presumably
outside the double membrane, indicates
that came after capture? Maybe
flagella penetrate double
membrane...perhaps were initialy inside
or partially inside and outside.
2) nucleus
division does not need to be recreated,
can be basically the same inherited
prokaryote cell division (perhaps with
minor adjustments), only within a cell
membrane.
3) conjugation already existed as a
form of exchanging DNA before the first
eukaryote, it is possible that a
complete bacterium could be taken in
through a pilus. Some eukaryotes like
spyrogrya still reproduce sexually
through conjugation.
4) DNA was splitting and
merging with conjugation in prokaryotes
before eukaryotes.
5) division of nucleus and
cytoplasm is different, just like
mitochondria, when the cytoplasm
divides is signalled by molecules (as
far as I know), and a nucleus may
divide without the cytoplasm dividing
(immediately or perhaps ever) in some
protists. (Clearly many metamonads have
multiple nuclei). It's interesting
that some metamonads have muliple
nuclei (mastigonts), because when they
reproduce it is all integrated, each
nuceli is rebuilt (as far as I know).
Maybe that shows how simple throwing
together nuclei and cytoplasm is for
DNA for put together and reproduce.
6) two layer
membrane around nucleus, is evidence of
a prokaryote being captured in a
vacuole.
7) happened for mitochondria,
chloroplasts, (and later red algae and
green algae), that is support for a
prokaryote similar to rikettsia, or
cyanobacteria being engulfed and
forming nucleus.
8) "all eukaryotic HSP70
homologs share in common with the
Gram-negative group of eubacteria a
number of sequence features that are
not present in any archaebacterium or
Gram-positive bacterium, indicating
their evolution from this group of
organisms."
9) Most genes related to the nucleus
are related to archaebacteria, while
those relating to the cytoplasm are
related to eubacteria.
Perhaps there was a long period of time
where the future eukaryote nucleus was
only an organelle, reproducing
initially like mitochondria and
chloroplasts do, by themselves, but
initiated by the nuclear duplication
and cytoplasmic division (check).
Somehow the binary division process of
the cytoplasm DNA and the binary
division process of the
nucleus-organelle had to merge into one
process.
Either the spindle chromosome
method (mitosis) evolved before or
after the nucleus-organelle has taken
over the cytoplasm building function.
As time continued, the process of
spindle separation evolved for the
nucleus-organelle. As time continued,
the building of the nucleus-organelle
was taken over by the cytoplasmic DNA,
still reproducing by binary fission.
I
could see how budding would be a
natural evolution for a cell nucleus
that starts as an organelle, is
reproduced by cytoplasm DNA and then
the DNA is tranfered back into the
nucleus-organelle. The
nucelus-organelle would then recreate
the entire cell inside the nucleus
(including the cytoplasm DNA
presumably), and presumably it would
burst out and continue to copy that
way. Perhaps budding prokaryotes were
budding eukaryotes that still had their
cytoplasm DNA that actually lost their
nucleus-organelle. Then budding
perhaps evolved into mitosis. I think
that mitosis is more similar to binary
division than budding is.
It seems clear that the
nucleus-organelle copied itself.
Potentially the same proteins that
initiate DNA duplication and cell
division for the cytoplasm DNA
simulteously initiate DNA duplication
and cell (nucleus-organelle) division
in the nucleus-organelle. So the
nucleus-organelle may have been exactly
like a mitochondrion for many years.
Although there are uncertainties, this
first eukaryote is thought to be a
member of the broad group of single
celled eukaryotes called "flagellates".
It is theorized that later will evolve
the unicellular "ameobozoid" and
"ciliate" groups. (this is a little
vague and I am not sure it really
covers algae, and the other alveolates,
but it does reduce the complexity of
protists)
[1]
http://www.regx.de/m_organisms.php#planc
to
source: http://www.regx.de/m_organisms.p
hp#plancto
[2]
http://www.mansfield.ohio-state.edu/~sab
edon/biol1080.htm
source: http://www.mansfield.ohio-state.
edu/~sabedon/biol1080.htm
single circular chromosome to linear
chromosomes.
Possibly the prokaryote ancestor of the
first eukaryote had linear chromosomes
since some prokaryotes (although very
few) are known to have linear
chromosomes instead of or in addition
to a single circular chromosome.
Perhaps a DNA
strand entered a cell by conjugation,
the circle of DNA was cut to insert the
new DNA (plasmid), but the new DNA
strand was not sewn back into the
original strand of DNA creating two
strands of DNA which eventually evolved
into the first 2 chromosomes.
Perhaps the first eukaryote nucleus was
a virus, many of which have linear
chromosomes.
This includes the evolution of
histones, proteins which are packed in
between nucleotides in each
chromosome.
Presumably DNA duplication (sythesis)
of chromosomes (in the nucleus) is
initially identical to DNA duplication
of DNA strands or circular DNA.
Some prokaryotes do not have just one
circle of DNA. Brucella melitensis
has 2 circlular chromosomes.
Agrobacterium tumefaciens has a
circular and a linear chromosome.
Streptomyces griseus can have one
linear chromosome. Borrelia
burgdorferi contains a linear
chromosome and a number of variable
circular and linear plasmids. Most
eukaryote orgenelles have a single
circular chromosome except for the
mitochondria of most cnidarians and
some other forms which have linear
chromosomes.
undulipodium) evolves on early single
cell eukaryotes.
The eukaryote cilia (flagella,
undulipodia) may evolve from a
prokaryote flagella connected to the
nucleus, from the cytoskeleten, or a
symbiotic prokaryote.
Cilia and eukaryote flagella are
structurally the same, but have minor
functional differences. Cilia are a
special class of eukaryote flagella.
The
eukarote flagellum is different from
prokayote flagellum. The prokaryote
flagallum is a solid structures, made
of the protein flagellin, which
protrudes through the plasma membrane.
The eukaryote flagellum (and cilium)
contains a "9 plus 2 array", 9
microtubules in a circle with 2
microtubules in the center. Some
people think that the eukaryote
flagella and cilia should be called
"undulipodia".
In some species the spindles used in
mitosis connect to the bases of the
eukaryote cilia (undulipodia), which
leads some people to think that the
spindles of mitosis may have evolved
from the eukaryote cilia.
Some people think that the eukaryote
cilium (flagellum, undulipodia) was a
spirochete (prokaryote) that formed a
symbiotic relationship with a eukaryote
host, whose DNA was transfered to the
host nucleus. Other possibilities are
that the eukaryote flagellum evolved
from prokaryote flagellum, or simply
evolved over time through natural
selection.
The eukaryote flagellum protein
"tubulin" is thought to be related to a
bacterial replication/cytoskeletal
protein "FtsZ" found in some
archaebacteria (archaea).
What method of reproduction this first
nucleated cell used is a great mystery.
Among the choices are binary division,
budding, or mitosis. My own feeling is
that budding or dual binary division
(both nucleus and cytoplasm) was how
this cell initially copied.
The eukaryote
flagellum (cilium, undulipodium) is the
same inherited and found on sperm
cells.
constantly synthesizing DNA and then
having a division period (as is the
case for all known prokaryotes), but
this cell has a period in between cell
division and DNA synthesis where DNA
synthesis is not performed. Later some
cells develop a stage after synthesis
and before cell division.
For the first time, a
cell is not constantly synthesizing DNA
(S) and then having a division period
(D) (as is the case for all known
prokaryotes), but this cell has a
period in between cell division and DNA
synthesis where DNA synthesis is not
performed (G1) . Later some cells
develop a stage after synthesis and
before cell division (G2).
a prokaryote, synchronized duplication
and division of organelle-nucleus and
cytoplasm of early eukaryote cell
evolves. Before this, eukaryote cell
division usually results in one cell
with no organelle-nuclei and a second
cell with 2 organelle-nuclei. Perhaps
the organelle-nuclei attach to the
outer cell membrane in the same way the
cytoplasmic DNA do, which allows new
cytoplasm growth to separate the two
organelle-nucleus in addition to the
cytoplasmic DNA.
Or perhaps the first
system of organized nuclei separation
originated with the organelle-nucleus
flagella microtubules grewing into the
cytoskeleton, and organized system
spindles and mitosis.
If the nuclear membrane was formed
around the DNA within a prokaryote,
then binary division had to adapt to
separate the duplicated DNA within the
proto-nucleus (not within the entire
cell) which may have been very simple
to evolve. If the cytoplasm grew
outside the cell wall of a prokaryote,
binary division would have to adapt to
separate that external cytoplasm.
source:
source:
haploid (single set of chomosomes)
eukaryote nucleus, evolves in
eukaryotes. Before mitosis, there is a
synthesis stage where DNA in the form
of chromosomes are duplicated in the
nucleus before the nucleus and cell
divide.
explain basic process of mitosis:
prophase,
metaphase, anaphase, telophase
Presumably no prokaryotes have ever
reproduced through mitosis. Only
eukaryotes reproduce asexually using
mitosis.
Most people accept that some protists
were sexual and later lost that
ability. But the majority view now is
that the first eukaryotes were asexual,
and that some protists still living now
have never had sexual ability.
Because mitosis is complex and similar
in detail in all species that do
mitosis, people think that mitosis only
evolved once, and was inherited by all
species that do mitosis.
The major differences between this new
method of copying, mitosis and the
older method, binary fission (add
budding?) are:
1) In mitosis, microtubule
spindles attach to the kinetochore (the
protein structure in eukaryotes which
assembles on the centromere and links
the chromosome to microtubule polymers
from the mitotic spindle during
mitosis) and pull apart the two DNA
copies, where in binary fission the DNA
(single chromosome) attaches to a part
of the cytoplasm which pulls apart the
two cells.
2) Chromosomes (linear pieces of
DNA), not a circle of DNA is being
copied.
People speculate that early mitosis had
spindles outside the nucleus, with
chromosomes fastened to the nuclear
membrane, as can still be seen in
parabasalia and dinoflagellates, which
appear to have primitive nuclei.
In more ancient species the nuclear
membrane persists through mitosis
(closed mitosis), but in more recent
species, like metazoa, land plants, and
many kinds of protists, the nuclear
membrane disintegrates before mitosis
and is rebuilt after (open mitosis).
Most people think that extranuclear
spindles (spindles that originate
outside of the nucleus) and closed
mitosis evolved first. Only later did
pleuromitosis (spindles rotate 90
degrees, nucleus can be semi-open, or
closed) and then orthomitosis (spindles
are on both sides of nucleus and
separate chromosomes in a straight
line, nucleus can be open, semi-open or
closed) evolve in later eukaryotes.
It is
interesting to think about how how
binary fission (or potentially budding)
of prokaryote cells with no nucleus
evolved into mitosis and the use of
spindles.
Mitosis, budding, and binary fission
are the only asexual methods of
reproduction known.
Perhaps mitosis evolved first only
copying the nucleus then later evolved
to make not only a new nucleus but also
a new cell around that nucleus.
[1] Mitosis divides genetic information
during cell division Source:
http://www.ncbi.nlm.nih.gov/About/primer
/genetics_cell.html This image is
from the Science Primer, a work of the
National Center for Biotechnology
Information, part of the National
Institutes of Health. As a work of the
U.S. federal government, the image is
in the public domain.
source: http://en.wikipedia.org/wiki/Mit
osis
[2] Prophase: The two round objects
above the nucleus are the centrosomes.
Note the condensed chromatin. from
Gray's Anatomy. Unless stated
otherwise, it is from the online
edition of the 20th U.S. edition of
Gray's Anatomy of the Human Body,
originally published in 1918. Online
editions can be found on Bartleby and
also on Yahoo!
source:
division evolves. Two eukaryote cells
can merge into one cell with 2 nuclei
and then divide back into single 1
nucleus cells.
Possibly two cells that fuse
cytoplasms but not nuclei, may still
retain the system of cytoplasmic DNA
and organelle-nucleus attachment to
cell membrane (wall?), but on each half
of the new cell, therefore making dual
haploid mitosis (potentially of both
cytoplasmic DNA and organelle-nucleus
in synchronized duplication) a simple
evolutionary next step.
syngamy, gametogamy) evolves in
protists. Haploid (1 set of
chromosomes) eukaryote cells merge and
then their nuclei merge (karyogamy) to
form the first diploid (2 sets of
chromosomes) cells (the first zygote).
This fusion of 2 haploid cells results
in the first diploid single-celled
organism, which then immediately
divides (both nucleus and cytoplasm by
single-division meiosis) back to two
haploid cells.
Possibly first, only cytoplasmic
merging happened with nuclear merging
(karyogamy) and nuclear division
(karyokinesis) evolving later.
Now, two cells
with different DNA can mix providing
more chance of variety/mutation. Two
chromosome sets provides a backup copy
of important genes (sequences that code
for proteins, or nucleic acids) that
might be lost with only a set of single
chromosomes.
The life cycle of future organisms will
now have two phases, a gamophase (from
n to 2n (until syngamy)), and zygophase
(from 2n to n (until meiosis)). Gamoid
cells are not haploid in polyploid
organisms.
Potentially sexual cell and genetic
fusion is what made the first eukaryote
cell, and sex in protists may be
directly descended from conjugation in
prokaryotes, in other words not evolved
from a different method independently
of conjugation, because some
metamonads, for example Saccinobaculus
reproduce sexually, and look very much
like a prokaryote sperm cell which
formed the nucleus captured in an ovum
cell.
For sexual species there are 3 basic
life cycles:
1) Haploid (Haplontic) life cycle:
zygotic meiosis. Life as haploid
cells, cell division immediately after
creation of zygote from fusion. (All
fungi, Some green algae, Many
protozoa)
2) Diploid (Diplontic) life cycle:
gametic meiosis. Instead of immediate
cell division, zygote reproduces by
mitosis. Haploid gametes never copy by
mitosis. (animals, some brown algae)
3)
Haplodiploid (Haplodiplontic,
Diplohaplontic, Diplobiontic) life
cycle: sporic meiosis. Diploid cell
(sporocyte) meiosis results in 2
haploid sporophytes (gamonts), not 2
haploid gametes. These haploid cells
then differentiate? or mitosis? to form
haploid gametes. Haplodiplontic
organisms have alternation of
generations, one generation involves
diploid spore-producing single or
multicellular sporophytes (makes
spores) and the other generation
involves haploid single or
multicellular gamete-producing
multicellular gametophytes (makes
gametes). Pants and many algae have
this haplodiplontic life cycle.
These first sexual cells are haplontic,
with zygotic meiosis; they reproduce
asexually through mitosis as haploid
cells, fusing to a diploid cell without
mitosis, then dividing back into
haploid cells.
An important evolutionary step evolves
here in that now two cells can
completely merge into one cell. This
merge not only includes their nuclei,
but also their cytoplasm (althought the
DNA do not merge). Before now, as far
as has ever been observed, no two cells
have ever completely merged, although,
through conjugation some prokaryotes
have been observed to exchange DNA.
This marks the beginning of the
"haplonic lifestyle" with "zygotic
meosis", where the organism is haploid
until cell fusion which is immediately
followed by (one-step) meiosis of the
zygote, after which the haploid cells
continues to reproduce through
mitosis.
Possibly the first sexual organism
merged through a form of "autogamy"
(both haploid gametes originate from
the same individual, the opposite of
"allogamy" where the gametes originate
from different individuals). Some
species reproduce by a form of autogamy
(intracellular autogamy), where nuclei
(also called pronuclei) divide and then
merge within the same cell before the
entire cell divides. Some metamonads
(earliest still living eukaryotes),
like Oxymonas and Saccinobaculus can
reproduce asexually by mitosis, but
also can reproduce sexually using this
form of autogamy. This may be evidence
that some prokaryote could also merge
two entire cells (if the eukaryote
nucleus was a prokaryote). Perhaps
prokaryotes evolved full cellular
fusion before the first eukaryote. If
that is true, then this initial form of
nuclei dividing and merging
(intracellular autogamy) may have
existed for some time before full
eukaryote cell merging and synchronized
eukayote nucleus and cytoplasm division
evolved. It is difficult to see what
selective advantage autogamy could
possibly have since no new DNA is ever
introduced into the next generation of
organism, as opposed to "allogamy",
where DNA from different individuals is
merged, and which has a clear selective
advantage. So perhaps autogamy evolved
after allogamy, although to me it
appears that allogamy is more complex
than autogamy, and autogamy would be a
perfect starting step to develop the
needed proteins and processes for the
more complicated allogamy (autogamy
only involves the duplication and
merging of two nuclei, where allogamy
involves the merging of the cell walls,
and cytoplasm in addition to the two
nuclei.)
This is the beginning of the label
"gamete" for haploid cells that can
merge to form a diploid zygote. In
addition, the label "gametocyte" or
"gamont" is any polyploid cell that
divides (meiosis) into haploid gamete
cells which can merge to form a zygote.
Perhaps
there is a relationship between
prokaryote spore formation and the
phenomenon of diploid zygotes forming a
thick cell wall.
Perhaps the first sex (full cell
nucleus and cytoplasm fusion) was
interchangeably isogamous (both gametes
are identical and interchangable), with
only one gender, in other words, the
first sex on earth was homosexual.
Then later heterogamous gametes
evolved, where there were two distinct
haploid gamete cells, usually a large
female cell and a smaller flagellated
male cell.
Sex also allows organisms to choose
reproductive partners that are more
likely to make new organisms that are
more likely to survive.
An alternative theory is that a failed
mitosis could result in a diploid
nucleus.
What advantage might autogamy of
intercellular nuclei have, the added
chance of mistakes in the merging of
two nuclei? In addition, why would
such a system (intracellular autogamy)
persist if there was no selective
advantage? Why wouldn't oxymonas or
saccinobacculus reduce totally to
asexual mitosis and or allogamous
sexual reproduction and either never
make use of or lose intracellular
autogamous sexual reproduction
completely?
This is the first eukaryote cell to
have a life cycle that involves two
different kinds of cells.
[1] Zygotic Meiosis. GNU
source: http://en.wikipedia.org/wiki/Ima
ge:Zygotic_meiosis.png
[2] Gametic Meiosis. GNU
source: http://en.wikipedia.org/wiki/Ima
ge:Gametic_meiosis.png
duplication and a cell division of a
diploid cell into 2 haploid cells)
evolves.
detail one-step meiosis:
The is no DNA crossover or chiasma
formation in one-division meiosis,
apparently because either duplication
of chromosomes or separation of
chromatids does not occurred.
As far as I know, mitosis and one-step
meiosis are the same with the only
exceptions that 1) in meiosis two
haploid cells join before cell
division, and 2) in mitosis the DNA is
duplicated before cell division, but in
meiosis the DNA is not duplicated
before cell division.
Meiosis can be one step (one DNA
duplication and then one cell division)
or two step (two DNA duplications and
then two divisions). Probably one step
meosis evolved first and two step
meiosis later.
Meiosis can only function on cells with
two or more sets of chromosomes.
The Protists
Pyrsonympha and Dinenympha has up to a
four step meiosis.
Because meiosis is similar and complex
in detail in all species that do
meiosis, people think that meiosis only
evolved once, and was inherited by all
species that do meiosis.
[1] GametoGenesis. COPYRIGHTED EDU
source: http://www.bio.miami.edu/dana/10
4/gametogenesis.jpg
[2] Sexual cycle oxymonas, identical
to saccinobaculus, one step meiosis.
haploid. COPYRIGHTED CANADA
source: http://www.zoology.ubc.ca/~redfi
eld/clevelan/oxymonas.GIF
2 haploid cells fuse) evolves.
This is required
for diploid mitosis.
Duplication of diploid DNA may be very
similar to duplication of haploid DNA.
Initially perhaps the diploid DNA
duplicated, but still divided in
one-division meiosis.
This begins the "diplontic" life cycle
(with gametic meiosis), where diploid
cells (a zygote) can copy asexually
through mitosis after merging. This
organism, when haploid, cannot do
mitosis (presumably haploid gamete
mitosis will evolve much later in brown
algae), and this is still true in all
descendents (including humans) of this
single celled organism.
The proteins and
mechanism of mitosis of diploid cells
is probably very similar to mitosis of
haploid cells. The most primitive
organisms still alive that are
diplontic are the metamonads (e.g.
Oxymonads: Notila, Hypermastigotes:
Urinympha, Macrospironympha,
Rhynchonympha).
(cell and nucleus fusion) between two
isogamous (same size) gametes but which
have 2 different (+ and -) forms
(genders).
Perhaps the invention of two different
genders originated when a flagellated
cell (or nucleus) divided by binary
division and only one half of the two
new cells retained the flagellum. Then
to differentiate the two cells even
more, but still keep the same DNA
template, different proteins could be
weighted on one half of the cell during
division to activate various operons in
one gender but not the other once the
two DNA pairs are separated.
Perhaps sex where the gametes are the
same size but cannot merge themselves
should be called "specific" or
"gendered" isogamy, and where any two
same sized gametes can merge called
"nonspecific" or "nongendered" isogamy.
between two different size gamete cells
(heterogamy or anisogamy) evolves in
protists.
Some species are heterogamous but two
of the same sized (gender) gametes can
fuse to form a zygote.
between one flagellated gamete and an
unflagellated gamete (oogamy, a form of
heterogamy) evolves in protists.
This system is
the system humans inherited.
sterols, molecules made by mitochondria
in eukaryotes) found in northwestern
Australia.
stromatolite, Zimbabwe.
[1] Fig. 2. Organic microstructure from
the Bulawaya stromatolite, Zimbabwe (ca
2.7 Ga). (a) TEM-micrograph from
demineralized rock section. (b) Laser
mass spectrum from individual specimen
of the same population (negative ions).
Field of measurement ca 1 small mu,
Greekm diameter. Attribution of
signals: 12: C−, 13: CH−,
14: CH−2, 16: O−, 17:
OH−, 19: F−, 24: C−2,
25: C2H−, 26: CN−, 28:
Si−, 36: C−3, 37:
C3H−, 40-42, 45: fragmental
carbonaceous groups, 48: C−4, 49:
C4H−, 50: C4H−2, 60:
SiO−2, resp. C−5, 61:
C5H−.
source: http://www.sciencedirect.com/sci
ence?_ob=MiamiCaptionURL&_method=retriev
e&_udi=B6VBP-42G6M5T-7&_image=fig5&_ba=5
&_user=4422&_coverDate=02%2F01%2F2001&_f
mt=full&_orig=browse&_cdi=5932&view=c&_a
cct=C000059600&_version=1&_urlVersion=0&
_userid=4422&md5=d9195635e48bcf1f817c009
69102189f
cyanobacteria, 2alpha -methylhopanes,
indicate that oxygenic photosynthesis
evolved well before the atmosphere
became oxidizing.
evolves.
Only a few species exhibit this
property (e.g. the Oxymonad Notilla,
Diatoms, Dasicladales {Acetabularia},
in many foraminiferans, and in
gregarines).
Gamontogamy may have evolved into
two-step meiosis.
The vast majority of eukaryotes living
now that reproduce sexually fuse
haploid cells. All "gametes" are
haploid cells that can merge, diploid
cells that can merge are gamonts.
Gamonts (Meiocytes) are cells that
produce gametes.
In theory this should be very similar
if not exactly like haploid cell
fusion, so perhaps this is not a major
evolutionary step.
[1] The Oxymonad, Notila (diploid
Pacific form) life cycle. COPYRIGHTED
source: http://www.zoology.ubc.ca/~redfi
eld/clevelan/notila.GIF
cell divisions with no stage in between
which result in one diplid cell
dividing into four haploid cells)
evolves.
Meiosis and mitosis are similar in
being process of nucleus and cell
division, but are different.
Differenc
es between meiosis and mitosis:
1) At least one
crossover per homologous pair happens
in 2 step meiosis but crossover usually
does not happen in mitosis.
2) Two step meiosis
involves cell divisions that happen one
after the other, where mitosis only
happens after one DNA duplication
(there are never 2 mitoses together
without a DNA duplication between them
to my knowledge).
The cell division in two step meiosis
that involves a separation of sister
chromatids (not homologous chromosome
pairs) is basically identical to
mitosis. For two step meiosis, this is
the second nucleus and cell division.
Later
multistep meiosis evolves, where there
may be as many as 4 divisions (for
example in the protists Pyrsonympha and
Dinenympha).
[1] GametoGenesis. COPYRIGHTED EDU
source: http://www.bio.miami.edu/dana/10
4/gametogenesis.jpg
[2] Sexual cycle oxymonas, identical
to saccinobaculus, one step meiosis.
haploid. COPYRIGHTED CANADA
source: http://www.zoology.ubc.ca/~redfi
eld/clevelan/oxymonas.GIF
(Thermus Aquaticus {used in PCR},
Deinococcus radiodurans {can survive
long exposure to radiation}) evolve
now.
PHYLUM Deinococcus-Thermus
CLASS Deinococci
ORDER Deinococcales
ORDER
Thermales
The Deinococcus-Thermus are a small
group of bacteria comprised of cocci
highly resistant to environmental
hazards. There are two main groups. The
Deinococcales include a single genus,
Deinococcus, with several species that
are resistant to radiation; they have
become famous for their ability to eat
nuclear waste and other toxic
materials, survive in the vacuum of
space and survive extremes of heat and
cold. The Thermales include several
genera resistant to heat. Thermus
aquaticus was important in the
development of the polymerase chain
reaction where repeated cycles of
heating DNA to near boiling make it
advantageous to use a thermo-stable DNA
polymerase enzyme. These bacteria have
thick cell walls that give them
gram-positive stains, but they include
a second membrane and so are closer in
structure to those of gram-negative
bacteria.
[1] D. radiodurans growing on a
nutrient agar plate. The red color is
due to carotenoid pigment. Links to
816x711-pixel, 351KB JPG. Credit: M.
Daly, Uniformed Services University of
the Health Sciences NASA
source: http://science.nasa.gov/newhome/
headlines/images/conan/D_rad_dish.jpg
[2] Photomicrograph of Deinococcus
radiodurans, from
www.ornl.gov/ORNLReview/ v34 The Oak
Ridge National Laboratory United
States Federal Government This work
is in the public domain because it is a
work of the United States Federal
Government. This applies worldwide. See
Copyright.
source: http://en.wikipedia.org/wiki/Ima
ge:Deinococcus.jpg
Eubacteria phylum, Cyanobacteria
(ancestor of all eukaryote chloroplasts
{plastids}) evolving now. There is a
conflict between the interpretation of
the geological and the genetic evidence
as to if oxygen photosynthesis and
cyanobacteria evolved earlier around
3800mybn or here at 2500mybn.
Cyanobacteria get
their energy from photosythesis.
Cyanobacteria include unicellular,
colonial, and filamentous forms. Some
filamentous cyanophytes form
differentiated cells, called
heterocysts, that are specialized for
nitrogen fixation, and resting or spore
cells called akinetes. Each individual
cell typically has a thick, gelatinous
cell wall, which stains gram-negative.
The cyanophytes lack flagella, but may
move about by gliding along surfaces.
Most are found in fresh water, while
others are marine, occur in damp soil,
or even temporarily moistened rocks in
deserts. A few are endosymbionts in
lichens, plants, various protists, or
sponges and provide energy for the
host.
Chloroplasts found in eukaryotes (algae
and higher plants) most likely
represent reduced endosymbiotic
cyanobacteria. This endosymbiotic
theory is supported by various
structural and genetic similarities.
Primary chloroplasts are found among
the green plants, where they contain
chlorophyll b, and among the red algae
and glaucophytes, where they contain
phycobilins. It now appears that these
chloroplasts probably had a single
origin. Other algae likely took their
chloroplasts from these forms by
secondary endosymbiosis or ingestion.
tenative:
CLASS Chroobacteria
CLASS Hormogoneae
CLASS
Gloeobacteria
Some live in the fur of sloths,
providing a form of camouflage.
[1] Oscillatoria COPYRIGHTED EDU
source: http://www.stcsc.edu/ecology/alg
ae/oscillatoria.jpg
[2] Lyngbya COPYRIGHTED EDU
source: http://www.stanford.edu/~bohanna
n/Media/LYNGB5.jpg
Non-Sulphur) evolve now.
PHYLUM Chloroflexi
CLASS Chloroflexi
CLASS Thermomicrobia
The Chloroflexi are a group of bacteria
that produce ATP through
photosynthesis. They make up the bulk
of the green non-sulfur bacteria,
though some are classified separately
in the Phylum Thermomicrobia. They are
named for their green pigment, usually
found in photosynthetic bodies called
chlorosomes.
Chloroflexi are typically filamentous,
and can move about through bacterial
gliding. They are facultatively
aerobic, but do not produce oxygen
during photosynthesis, and have a
different method of carbon fixation
than other photosynthetic bacteria.
Phylogenetic trees indicate that they
had a separate origin.
[1] Chloroflexus photomicrograph from
Doe Joint Genome Institute of US Dept
Energy PD
source: http://en.wikipedia.org/wiki/Ima
ge:Chlorofl.jpg
Era.
appear in many places.
million years starts now.
nucleus that makes ribosomes, evolves.
In some
eukaryotes (thought to be more
ancient), the nucleolus just divides
during mitosis, but in other eukaryotes
the mitosis is dissolved and rebuilt
after nuclear division.
In euglenids, kinetoplastids,
dinoflagellates, some amoebae and some
coccidians, the nucleolus remains
visible throughout mitosis and divides
into two, but in the majority of groups
the nucleolus dissapears and reforms at
telophase. That the nucleolus can
divide by itself suggests that it was
once a free living cell.
[1] Nucleolus, COPYRIGHTED
source: http://www.eccentrix.com/members
/chempics/Slike/cell/Nucleolus.jpg
[2] With the combination of x-rays
from the Advanced Light Source and a
new protein-labeling technique,
scientists can see the distribution of
the nucleoli within the nucleus of a
mammary epithelial cell. USG PD
source: http://www.lbl.gov/Science-Artic
les/Archive/xray-inside-cells.html
reticulum evolves in eukaryote cell.
Rough
and smooth endoplasmic reticulum
evolves in eukaryote cell.
The rough ER manufactures and
transports proteins destined for
membranes and secretion. It synthesizes
membrane, organellar, and excreted
proteins. Minutes after proteins are
synthesized most of them leave to the
Golgi apparatus within vesicles. The
rough ER also modifies, folds, and
controls the quality of proteins.
The smooth ER has functions in several
metabolic processes. It takes part in
the synthesis of various lipids (e.g.,
for building membranes such as
phospholipids), fatty acids and
steroids (e.g., hormones), and also
plays an important role in carbohydrate
metabolism, detoxification of the cell
(enzymes in the smooth ER detoxify
chemicals), and calcium storage. It
also is a large transporter of nutrient
found in each cell.
[1] Figure 1 : Image of nucleus,
endoplasmic reticulum and Golgi
apparatus. (1) Nucleus. (2) Nuclear
pore. (3) Rough endoplasmic reticulum
(RER). (4) Smooth endoplasmic reticulum
(SER). (5) Ribosome on the rough ER.
(6) Proteins that are transported. (7)
Transport vesicle. (8) Golgi apparatus.
(9) Cis face of the Golgi apparatus.
(10) Trans face of the Golgi apparatus.
(11) Cisternae of the Golgi
apparatus. I am the copyright holder
of that image (I might even have the
CorelDraw file around somewhere:-), and
I hereby place the image and all
partial images created from it in the
public domain. So, you are free to use
it any way you like. In fact, I am
delighted that one of my drawings makes
it into print! I can mail you the
.cdr file, if you like (and if I can
find it), if you need a better
resolution for printing. Yours, Magnus
Manske Source: [1]. See also
User:Magnus Manske
source: http://en.wikipedia.org/wiki/Ima
ge:Nucleus_ER_golgi.jpg
dictyosome) evolves in eukaryote cell.
The
primary function of the Golgi apparatus
is to process proteins targeted to the
plasma membrane, lysosomes or
endosomes, and those that will be
formed from the cell, and sort them
within vesicles. It functions as a
central delivery system for the cell.
Most of the transport vesicles that
leave the endoplasmic reticulum (ER),
specifically rough ER, are transported
to the Golgi apparatus, where they are
modified, sorted, and shipped towards
their final destination. The Golgi
apparatus is present in most eukaryotic
cells, but tends to be more prominent
where there are many substances, such
as proteins, being secreted. For
example, plasma B cells, the
antibody-secreting cells of the immune
system, have prominent Golgi complexes.
[1] Figure 1: Image of nucleus,
endoplasmic reticulum and Golgi
apparatus: (1) Nucleus, (2) Nuclear
pore, (3) Rough endoplasmic reticulum
(RER), (4) Smooth endoplasmic reticulum
(SER), (5) Ribosome on the rough ER,
(6) Proteins that are transported, (7)
Transport vesicle, (8) Golgi apparatus,
(9) Cis face of the Golgi apparatus,
(10) Trans face of the Golgi apparatus,
(11) Cisternae of the Golgi apparatus,
(12) Secretory vesicle, (13) Plasma
membrane, (14) Exocytosis, (15)
Cytoplasm, (16) Extracellular space.
source: http://en.wikipedia.org/wiki/Ima
ge:Nucleus_ER_golgi_ex.jpg
makes lysosomes which fuse with
endosomes. The various molecules in
lysosomes digest the contents of the
endosome, which then exits the cell as
waste.
[1] Figure 1: Image of nucleus,
endoplasmic reticulum and Golgi
apparatus: (1) Nucleus, (2) Nuclear
pore, (3) Rough endoplasmic reticulum
(RER), (4) Smooth endoplasmic reticulum
(SER), (5) Ribosome on the rough ER,
(6) Proteins that are transported, (7)
Transport vesicle, (8) Golgi apparatus,
(9) Cis face of the Golgi apparatus,
(10) Trans face of the Golgi apparatus,
(11) Cisternae of the Golgi apparatus,
(12) Secretory vesicle, (13) Plasma
membrane, (14) Exocytosis, (15)
Cytoplasm, (16) Extracellular space.
source: http://sun.menloschool.org/~cwea
ver/cells/e/lysosomes/
source: http://en.wikipedia.org/wiki/Ima
ge:Nucleus_ER_golgi_ex.jpg
that can only live in other bacteria,
closely related to Rickettsia
prowazekii, an aerobic
alpha-proteobacteria that causes
louse-borne typhus, enters an early
eukaryote cell. As time continues a
symbiotic relationship evolves, where
the Rickettsia forms the mitochondria,
organelles of every euokaryote cell.
The mitochondria perform the Acid
Citric Cycle (Krebs Cycle), using
oxygen to breakdown glucose into CO2
and H2O, and provide up 38 ATP
molecules. Mitochondria reproduce by
themselves, and are not created by the
DNA in the cell nucleus. As time
continues some of the DNA from the
mitochondria merges with the cell
nucleus DNA. Mitochondria produce
sterol used to make the eukaryote cell
wall flexible. Because mitochondria
need Oxygen, but the level of oxygen is
very low on earth, oxygen may be
provided by photosynthesizing
cyanobacteria living near these cells.
All eukaryotes alive today either have
mitochondria except the amitochondriate
excavates (metamonads), the most
ancient of the eukaryotes alive today.
That parabasalids have hydrogenosomes,
anaerobic organelles that seem to have
evolved from mitochondria, many people
think amitochondriate species lost
their mitochondria over time.
This changes
the eukaryote cell from an anaerobic to
aerobic unicellular organism.
This early
mitochondria may have "tubular
christae".
Perhaps there was a period of time
where a system evolved to make sure
both halves received mitochondria
during cell division.
Protists with discoidal mitochondrial
cristea will later evolve from the
Bikont tubular mitochondrial christae
branch.
For the most part:
1) Excavates, Amoebozoa,
and Chromealveolates have or had
tubular christae,
2) Discicristata
(Euglenozoa) have discoidal christae.
3)
Cryptomonads, Glaucophytes, Red Algae,
Green Algae, Plants, Fungi, Animals all
have flat christae.
From this point on, all eukaryotes will
need Oxygen to use mitochondria and
receive the ATP made by mitochondria.
O
ne theory is that, as more O2 is
produced at the surface of the ocean,
protists (which require oxygen for
mitochondria) can move to the ocean
floor.
[1] Phylogenetic hypothesis of the
eukaryotic lineage based on
ultrastructural and molecular data.
Organisms are divided into three main
groups distinguished by mitochondrial
cristal shape (either discoidal,
flattened or tubular). Unbroken lines
indicate phylogenetic relationships
that are firmly supported by available
data; broken lines indicate
uncertainties in phylogenetic
placement, resolution of which will
require additional data. Color coding
of organismal genus names indicates
mitochondrial genomes that have been
completely (Table 1), almost completely
(Jakoba, Naegleria and
Thraustochytrium) or partially (*)
sequenced by the OGMP (red), the FMGP
(black) or other groups (green). Names
in blue indicate those species whose
mtDNAs are currently being sequenced by
the OGMP or are future candidates for
complete sequencing. Amitochondriate
retortamonads are positioned at the
base of the tree, with broken arrows
denoting the endosymbiotic origin(s) of
mitochondria from a Rickettsia-like
eubacterium. Macrophar.,
Macropharyngomonas.
source: http://nar.oxfordjournals.org/co
ntent/vol26/issue4/images/gkb18201.gif
[2] Figure 1 Phylogenetic tree of
eukaryotes based on ultrastructural and
molecular data. Organisms are
sub-divided into main groups as
discussed in the text. Only a few
representative species for which
complete (or almost complete) mtDNA
sequences are known are shown in each
lineage. In some cases, line drawings
or actual pictures of the organisms are
provided (Acanthamoeba, M. Nagata; URL:
http://protist.i.hosei.ac.jp/PDB/PCD3379
/htmls/21.html; Allomyces, Tom Volk;
URL:
http://botit.botany.wisc.edu/images/332/
Chytridiomycota/Allomyces_r_So_pa/A._arb
uscula_pit._sporangia_tjv.html;
Amoebidium, URL:
http://cgdc3.igmors.upsud.fr/microbiolog
ie/mesomycetozoaires.htm; Marchantia,
URL:
http://www.science.siu.edu/landplants/He
patophyta/images/March.female.JPEG
Scenedesmus, Entwisle et al.,
http://www.rbgsyd.gov.au/_data/page/1824
/Scenedesmus.gif). The color-coding of
the main groups (alternating between
dark and light blue) on the outer
circle corresponds to the color-coding
of the species names. Unbroken lines
indicate phylogenetic relationships
that are firmly supported by available
molecular data; broken lines indicate
uncertainties in phylogenetic
placement, resolution of which will
require additional sequence data. [t:
why not color code or add which type of
mito?]
source: http://arjournals.annualreviews.
org/doi/full/10.1146/annurev.genet.37.11
0801.142526
Unikonts (one cilium). Bikonts (also
called anterokonts for having anterior
{forward facing} cilia) will evolve
into the vast majority of the Protist
and all of the Plant Kingdoms. The
Unikonts will evolve into the ameobozoa
(tenatively), and the opisthokonts
(ancestrally posterior cilium) which
include the entire Fungi and Animal
Kingdoms.
Since members of both the unikont
(animals, fungi) and bikont
(metamonads, plants) can reproduce
sexually, sex had to evolve before this
branching, presuming sexual
reproduction is strictly inherited and
did not evolve twice.
[1] Figure 1. Phylogenetic hypothesis
of the eukaryotic lineage based on
ultrastructural and molecular data.
Organisms are divided into three main
groups distinguished by mitochondrial
cristal shape (either discoidal,
flattened or tubular). Unbroken lines
indicate phylogenetic relationships
that are firmly supported by available
data; broken lines indicate
uncertainties in phylogenetic
placement, resolution of which will
require additional data. Color coding
of organismal genus names indicates
mitochondrial genomes that have been
completely (Table 1), almost completely
(Jakoba, Naegleria and
Thraustochytrium) or partially (*)
sequenced by the OGMP (red), the FMGP
(black) or other groups (green). Names
in blue indicate those species whose
mtDNAs are currently being sequenced by
the OGMP or are future candidates for
complete sequencing. Amitochondriate
retortamonads are positioned at the
base of the tree, with broken arrows
denoting the endosymbiotic origin(s) of
mitochondria from a Rickettsia-like
eubacterium. Macrophar.,
Macropharyngomonas.
source:
a mineral that cannot exist for much
time if exposed to oxygen, indicating
that free oxygen is accumulating in the
air of earth for the first time.
on land, begin here and are evidence of
more free oxygen in the air of earth.
[1]
http://www.kgs.ukans.edu/Extension/redhi
lls/redhills.html
source:
oldest line of eukaryotes still in
existence, the oldest living protists,
in the Phylum "Metamonada" (Excavates)
originating now. This is where the
eukaryote line is created and separates
from the archaebacteria (archaea) line.
Most of these species have an
excavated ventral feeding groove, and
all lack mitochondria. Mitochondria
are thought to have been lost
secondarily, although this is not
certain.
PHYLUM Metamonada
ORDER Carpediemondida
ORDER
Diplomonadida
ORDER Retortamonadida
CLASS Parabasalia
ORDER
Trichomonadida
ORDER Hypermastigida
CLASS Anaeromonada
ORDER Oxymonadida
ORDER Trimastigida
Includes Diplomonad
"Giardia", and Parabasalid "Trichomonas
vaginalis".
The trophozoite form of Giardia does
age and die.
Most Metamonads reproduce
asexually through closed (the nuclear
membrane does not dissolve during
mitosis) mitosis (and involves an
external spindle? is pluromitosis?),
but some species are "faculatively
sexual" (can reproduce sexually in
addition to asexually). So already by
the time of these most ancient of the
now living eukaryotes, sex had evolved.
eat bacteria?
Some people have this phylum as
part of the group "Excavates" which
includes the Phyla (Metamonada,
Percolozoa, and Euglenozoa).
The classification of the protists is
far from complete and settled. There
are currently more than one existing
classification scheme for the protists.
features of parabasalia and metamonada:
gamete type: flagellated
haplontic and
diplontic
condensed chromosomes in some
species
mitotic spindle:
parabasalia:
external
metamonadea: internal
polar
structures:
parabasalia: flagellar
root
metamonadea: kinetosome
flagella:
parabasalia: 4 to many
metamonadea: 2,4
heterokont, isokont, anisokont:
anisokont (Anisokont flagella are
those flagella that are unequal in
length, form, or direction. ) (Isokont
flagella are those flagella that are
equal in length, form, and direction.)
(The name heterokont refers to the
characteristic form of these cells,
which typically have two unequal
flagella. The anterior or tinsel
flagellum is covered with lateral
bristles or mastigonemes, while the
other flagellum is whiplash, smooth and
usually shorter, or sometimes reduced
to a basal body. The flagella are
inserted subapically or laterally, and
are usually supported by four
microtubule roots in a distinctive
pattern. )
flagellate stages: trophic
life
forms:
unicellular: flagellated
multice
llular: none
cell covering: naked
[1] Giardia lamblia, a parasitic
flagellate that causes giardiasis.
Image from public domain source at
http://www.nigms.nih.gov/news/releases/i
mages/para.jpg
source: http://www.nigms.nih.gov/news/re
leases/images/para.jpg
[2] . The cysts are hardy and can
survive several months in cold water.
Infection occurs by the ingestion of
cysts in contaminated water, food, or
by the fecal-oral route (hands or
fomites) . In the small intestine,
excystation releases trophozoites (each
cyst produces two trophozoites) .
Trophozoites multiply by longitudinal
binary fission, remaining in the lumen
of the proximal small bowel where they
can be free or attached to the mucosa
by a ventral sucking disk .
Encystation occurs as the parasites
transit toward the colon. The cyst is
the stage found most commonly in
nondiarrheal feces . Because the cysts
are infectious when passed in the stool
or shortly afterward, person-to-person
transmission is possible. While
animals are infected with Giardia,
their importance as a reservoir is
unclear.
source: http://www.dpd.cdc.gov/dpdx/HTML
/Giardiasis.asp?body=Frames/G-L/Giardias
is/body_Giardiasis_page1.htm
shows the eubacteria and archaebacteria
line separating here at 2,156 mybn,
first archaebacteria.
Eukaryote Phylum "Loukozoa" (Jakobea
and Malawimonadea) originating now.
These species have mitochondria with
tubular cristae, and are the most
ancient species that still have
mitochondria.
This species is the most ancient known
species to have a shell. This first
hard shells (lorika) made of calcium
carbonate (Calcite CaCO3), plates of
silica (SiO2), or carbon-based
molecules evolve around the
single-celled species living in the
ocean.
Perhaps this shell served to protect
the cell from external damage from
being eaten by other eukaryotes
(zooplankton), infection by bacteria or
viruses, control of buoyancy, to filter
UV light, against damage by non-living
sources.
Jakobids and Malawimonads are
also grouped as Excavates because they
have a ventral feeding groove.
Jakobids are flagellates with two
flagella located at the anterior end of
a ventral feeding groove (i.e., are
excavate), with mitochondria, freely
swimming or loricate (with protective
shell).
Flagellar apparatus with two basal
bodies giving rise to two major
microtubular roots, which support the
margins of the ventral groove. Other
cytoskeletal microtubules arise
directly or indirectly from the basal
bodies, no extrusomes.
Jakobids have tubular mitochondrial
cristae (transforming to flat cristae
in Jakoba libera). (1) This indicates
that flat evolved from tubular
cristae.
PHYLUM Loukozoa
ORDER Jakobida
ORDER
Malawimonadida
Reproduction=mitosis?
ORDER Jakobida
FAMILY Histionidae
The jakobid family
"Histionidae" reproduce asexually by
binary fission. In this family no
sexual reproduction has been observed
yet. (1)
FAMILY Jakobidae
[1] Histiona. This drawing was made by
D. J. Patterson. COPYRIGHTED EDU
source: http://microscope.mbl.edu/script
s/microscope.php?func=imgDetail&imageID=
3479
[2] Histiona (hist-ee-own-a) is a
jakobid flagellate related to Jakoba.
As with other excavates, there is a
ventral groove and the flagella insert
at the head of the groove. There are
two flagella, one lying in the groove
and one curving outwards from the point
of insertion. The margins of the groove
can be mistaken for flagella. Unlike
most other excavates, Histiona sits in
a stalked lorica when feeding. Lorica
with a cyst is evident. Phase contrast.
This picture was taken by David
Patterson, Linda Amaral Zettler, Mike
Peglar and Tom Nerad from cultures and
other materials maintained at the
American Type Culture Collection during
2001. COPYRIGHTED EDU
source: http://microscope.mbl.edu/script
s/microscope.php?func=imgDetail&imageID=
435
mitochondria split from the tubular
christae line.
This is the origin of the
Discicristata: species that have
discoid mitochondrial cristae and, in
some cases, a deep (excavated) ventral
feeding groove.
The Discicristata are Acrasid
slime molds, vahlkampfiid amoebas,
euglenoids, trypanosomes, and
leishmanias.
[1] Figure 1. Phylogenetic hypothesis
of the eukaryotic lineage based on
ultrastructural and molecular data.
Organisms are divided into three main
groups distinguished by mitochondrial
cristal shape (either discoidal,
flattened or tubular). Unbroken lines
indicate phylogenetic relationships
that are firmly supported by available
data; broken lines indicate
uncertainties in phylogenetic
placement, resolution of which will
require additional data. Color coding
of organismal genus names indicates
mitochondrial genomes that have been
completely (Table 1), almost completely
(Jakoba, Naegleria and
Thraustochytrium) or partially (*)
sequenced by the OGMP (red), the FMGP
(black) or other groups (green). Names
in blue indicate those species whose
mtDNAs are currently being sequenced by
the OGMP or are future candidates for
complete sequencing. Amitochondriate
retortamonads are positioned at the
base of the tree, with broken arrows
denoting the endosymbiotic origin(s) of
mitochondria from a Rickettsia-like
eubacterium. Macrophar.,
Macropharyngomonas.
source: http://nar.oxfordjournals.org/co
ntent/vol26/issue4/images/gkb18201.gif
Diplobiontic) life cycle (organism with
both diploid and haploid "alternate
life stages" that reproduce asexually
by mitosis) with "sporic meiosis"
evolves.
In this life cycle haploid gametes fuse
to form a diploid zygote which divides
by meiosis producing haploid spores
that produce (differentiate?) gametes,
starting the cycle again.
Initially these species are single
celled in both stages (like
Haptophyta).
All plants, most brown algae,
blastocladiid chytrids, many red algae,
and some filamentous green algae (e.g.
Cladophora) and foraminifera have
haplodiploid life cycles.
Initially, these organisms are single
celled, but later the mitosis stages
will become multicellular when the
cells that result from mitosis stick
together. The only? example of this
is Haptophyta, where diploid cells
divide in sporic meiosis, into haploid
cells (gamonts) which then divide into
gametes.
Of the diplohaplonic species, those
where the haploid and diploid stages
look the same are called "isomorphic"
and those where the two stages look
different are called "heteromorphic".
In land plants the haploid
(gametophyte) stage is reduced to only
a few cells. Since double DNA
chromosomes (diploid) provides more
possibilities than a single chromosome,
diploid organisms have a selective
advantage over haploid organisms.
[1] Figure 23.1.Plants have
haplodiplontic life cycles that involve
mitotic divisions (resulting in
multicellularity) in both the haploid
and diploid generations (paths A and
D). Most animals are diplontic and
undergo mitosis only in the diploid
generation (paths B and D).
Multicellular organisms with haplontic
life cycles follow paths A and C.
COPYRIGHTED EDU
source: http://zygote.swarthmore.edu/pla
ntfig1.gif
[2] Drawn by self for Biological life
cycle Based on Freeman & Worth's
Biology of Plants (p. 171). GNU
source: http://en.wikipedia.org/wiki/Ima
ge:Sporic_meiosis.png
with flat christae evolve from those
with tubular christae.
[1] Figure 1. Phylogenetic hypothesis
of the eukaryotic lineage based on
ultrastructural and molecular data.
Organisms are divided into three main
groups distinguished by mitochondrial
cristal shape (either discoidal,
flattened or tubular). Unbroken lines
indicate phylogenetic relationships
that are firmly supported by available
data; broken lines indicate
uncertainties in phylogenetic
placement, resolution of which will
require additional data. Color coding
of organismal genus names indicates
mitochondrial genomes that have been
completely (Table 1), almost completely
(Jakoba, Naegleria and
Thraustochytrium) or partially (*)
sequenced by the OGMP (red), the FMGP
(black) or other groups (green). Names
in blue indicate those species whose
mtDNAs are currently being sequenced by
the OGMP or are future candidates for
complete sequencing. Amitochondriate
retortamonads are positioned at the
base of the tree, with broken arrows
denoting the endosymbiotic origin(s) of
mitochondria from a Rickettsia-like
eubacterium. Macrophar.,
Macropharyngomonas.
source: http://nar.oxfordjournals.org/co
ntent/vol26/issue4/images/gkb18201.gif
primitive living members of the Phylum
"Euglenozoa" (euglenids, leishmania,
trypanosomes, kinetoplastids) evolved
at this time.
This is the oldest eukaryote to exhibit
colonialism. Perhaps eukaryote
colonialism is partially or fully
inherited from prokaryotes, but
colonialism may have evolved
independently again in eukaryotes.
This is the most ancient species known
to have a cell covering, which is of
the type "pellicle".
No examples of sexual
reproduction in the group have been
found. Reproduction is through closed
mitosis and involves an internal
spindle. At least one account of a
sexual cycle has been reported in
Scytomonas.
The chloroplasts are contained in three
membranes and are pigmented similarly
to the plants, suggesting they were
retained from some captured green
alga.
All Euglenozoa have mitochondria with
discoid cristae, which in the
kinetoplastids characteristically have
a DNA-containing granule or kinetoplast
associated with the flagellar bases.
I think
they are still haploid, mitosis
duplicates in nucleus?
Euglenozoa age?
This group is sometimes called
"Discicristates" because all members
have mitochondria with "discoidal
cristae".
Euglenids are the first eukaryotes with
an eyespot. Most colored euglenids
also have a stigma or eyespot, which is
a small splotch of red pigment on one
side of the flagellar pocket. This
shades a collection of light sensitive
crystals near the base of the leading
flagellum, so the two together act as a
sort of directional eye. Euglenozoa
eyepots evolved from chloroplasts.
This is the beginning of a light
sensory system which evolves to eyes?
A small number of euglinids have
chloroplasts and can photosynthesize.
In these species, the chloroplasts
contain three membranes and are thought
to have evolved at least 900 million
years later from a captured green alga.
Euglenoids, however, share reproductive
habits with their kinetoplastid
relations by reproducing mainly by
asexual binary fission. Euglenoids
reproduce very rapidly, absorbing their
flagellum and dividing haploid cells
through mitosis. Mitosis produces 4-8
flagellated haploid cells, called
zoospores. The zoospores then break out
of the parent cell and grow to full
size.
condensed chromosomes: yes in all
kinetoplasts, and some euglenophyta.
pol
ar structures: none
number of flagella:
kinetoplastids=(1 in some) 2,
euglenophyta=2 (4 in some)
life forms:
unicellular: flagellated
multicellular:
colonial
cell covering: pellicle
2. Euglenoids are small (10-500
µm) freshwater unicellular organisms.
3.
One-third of all genera have
chloroplasts; those that lack
chloroplasts ingest or absorb their
food.
4. Their chloroplasts are
surrounded by three rather than two
membranes.
a. Their chloroplasts
resemble those of green algae.
b.
They are probably derived from a green
algae through endosymbiosis.
5. The pyrenoid
outside the chloroplast produces an
unusual type of carbohydrate polymer
(paramylon)
not seen in green algae.
6. They possess two flagella, one of
which typically is much longer and than
the other and projects
out of a
vase-shaped invagination; it is called
a tinsel flagellum because it has hairs
on it.
7. Near the base of the
longer flagellum is a red eyespot that
shades a photoreceptor for detecting
light.
8. They lack cell walls, but
instead are bounded by a flexible
pellicle composed of protein strips
side-by-side.
9. A contractile vacuole,
similar to certain protozoa, eliminates
excess water.
10. Euglenoids reproduce
by longitudinal cell division; sexual
reproduction is not known to occur.
PHYLUM Euglenozoa
CLASS Euglenoidea
CLASS Diplonemea
CLASS
Kinetoplastea
CLASS Postgaardea
Those Euglnozoa that do not
photosynthesize feed on bacteria
(phagocytosis) or feed through
absorption (osmosis) of nutrients.
Most are small,
around 15-40 µm in size, although many
euglenids get up to 500 µm long.
Most Euglenozoa have two flagella,
usually one leading and one trailing.
Some euglenozoa cause parasitic disease
in other species.
A kinetoplastid member of
Euglenozoa, such as trypanosoma brucei
which causes African sleeping sickness,
is transmitted from host to host by a
vector, most commonly the tsetse fly.
In
most forms there is an associated
cytostome (mouth) supported by one of
three microtubule groups that arise
from the flagellar bases.
Average life cycle=? days
Average age of
euglenozoa life=? days
Trypanosomes (Kinetoplastids) typically
have complex life-cycles involving more
than one host, and go through various
morphological stages.
1000 Species of Euglenoids
(euglenophyta).
[1] euglena
source: http://www.fcps.k12.va.us/Stratf
ordLandingES/Ecology/mpages/euglena.htm
[2] euglena
source: http://protist.i.hosei.ac.jp/PDB
/Images/Mastigophora/Euglena/genus1L.jpg
Phylum "Percolozoa" (also called
"Heterolobosea") (acrasid slime molds)
evolved at this time.
Percolozoa are a group
of heterotrophic colourless protozoa,
including many that can transform
between amoeboid, flagellate, and
encysted stages. These are collectively
referred to as amoeboflagellates,
schizopyrenids, or vahlkampfids. They
also include the acrasids, a group of
social amoebae that aggregate to form
sporangia.
Very closely related to Euglenozoa.
All
characteristics are like Euglenozoa:
Percolozoa
have mitochondria with discoid
christae.
No examples of sexual reproduction in
the group have been found.
Reproduction is through closed mitosis
and involves an internal spindle.
No
chloroplasts (check) or (The
chloroplasts are contained in three
membranes and are pigmented similarly
to the plants, suggesting they were
retained from some captured green
alga.)
I think they are still haploid, mitosis
duplicates in nucleus?
Percolozoa age?
Percolozoa
are sometimes included in the group
"Discicristates" because all members
have mitochondria with "discoidal
cristae".
No eyespots.
closed mitosis with internal spindle.
The Percolozoa are the most ancient
species to have members that move by
pseudopodia, like amoeba.
PHYLUM Percolozoa
CLASS
Heterolobosea
ORDER Schizopyrenida Singh, 1952
ORDER Acrasida Shröter, 1886
(acrasids, cellular slime molds)
ORDER
Lyromonadida Cavalier-Smith, 1993
CLASS
Percolatea
ORDER Acrasida (acrasids, cellular
slime molds):
a. Cellular slime
molds (Phylum Acrasiomycota) (ORDER
Acrasida) exist as individual amoeboid
cells. (Plasmodial slime molds,
mycetozoa, which evolve later, exist as
a plasmodium. )
b. They live
in soil and feed on bacteria and
yeast.
c. As food runs out,
amoeboid cells release a chemical that
causes them to aggregate into a
pseudoplasmodium.
d. The pseudoplasmodium
stage is temporary; it gives rise to
sporangia that produce spores.
e.
Spores survive until more favorable
environmental conditions return; then
they germinate.
f. Spore germinate to
release haploid amoeboid cells, which
is again the beginning of asexual
cycle.
g. Asexual cycle occurs
under very moist conditions.
Percolozoa
feed on bacteria (phagocytosis) or
feed through absorption (osmosis) of
nutrients. (check)
Most are small, around 15-40
µm in size, although many euglenids
get up to 500 µm long.
The flagellate stage is slightly
smaller, with two or four anterior
flagella anterior to the feeding
groove.
Average life cycle=? days
Average age of
Percolozoa life=? days
Most Percolozoa are found as
bacterivores in soil, freshwater, and
on feces. There are a few marine and
parasitic forms, including the species
Naegleria fowleri, which can become
pathogenic in humans and is often
fatal. The group is closely related to
the Euglenozoa, and share with them the
unusual though not unique
characteristic of having mitochondria
with discoid cristae. The presence of a
ventral feeding groove in the
flagellate stage, as well as other
features, suggests that they are part
of the excavate group.
The amoeboid stage is roughly
cylindrical, typically around 20-40
μm in length. They are
traditionally considered lobose
amoebae, but are not related to the
others and unlike them do not form true
lobose pseudopods. Instead, they
advance by eruptive waves, where
hemispherical bulges appear from the
front margin of the cell, which is
clear. The flagellate stage is slightly
smaller, with two or four anterior
flagella anterior to the feeding
groove.
Usually the amoeboid form is taken when
food is plentiful, and the flagellate
form is used for rapid locomotion.
However, not all members are able to
assume both forms. The genera
Percolomonas, Lyromonas, and
Psalteriomonas are known only as
flagellates, while Vahlkampfia,
Pseudovahlkampfia, and the acrasids do
not have flagellate stages. As
mentioned above, under unfavourable
conditions, the acrasids aggregate to
form sporangia. These are superficially
similar to the sporangia of the
dictyostelids, but the amoebae only
aggregate as individuals or in small
groups and do not die to form the
stalk.
The Heterolobosea were first defined by
Page and Blanton in 1985 as a class of
amoebae, and so only included those
forms with amoeboid stages.
Cavalier-Smith created the phylum
Percolozoa for the extended group,
together with the enigmatic flagellate
Stephanopogon. (currently I have
stephanopogon colpoda images under
ciliates...) He maintained the
Heterolobosea as a class for amoeboid
forms, but most others have expanded
them to include the flagellates as
well.
Stephanopogon closely resembles certain
ciliates and was originally classified
with them, but is now considered a
flagellate.
[1] Stages of Naegleria fowleri, a
member of the Percolozoa. Adapted from
Image:Free-living amebic
infections.gif, which is from the CDC.
PD
source: http://en.wikipedia.org/wiki/Ima
ge:Naegleria.png
[2] CLASS Heterolobosea ORDER
Schizopyrenida Heteramoeba: The
flagellated form is large (30
�m), two flagella, an elongate
cytostome curving around the anterior
of the cell and forming a groove.
Nucleus with peripheral chromatin.
Probably feeds and divides as a
flagellate. One species. This genus is
most like Paratetramitus from which it
can be distinguished by peripheral
location of chromatin material. Cysts
without pores, excystment through a
weak region of wall. Marine.
Heteramoeba (het-err-a-me-ba) a naked
heterolobose amoeba, distinguished from
other types of naked amoebae with
lobose pseudopodia largely by
ultrastructural features, but trophic
heterolobose amoebae tend to form their
pseudopodially suddenly rather than
progressively. Phase contrast. This
picture was taken by David Patterson,
Linda Amaral Zettler, Mike Peglar and
Tom Nerad from cultures and other
materials maintained at the American
Type Culture Collection during 2001.
NONCOMMERCIAL USE
source: http://microscope.mbl.edu/script
s/microscope.php?func=imgDetail&imageID=
413
protist.
Multicellularity is a very important
event in the evolution of life on
earth. With multicellular organisms,
larger sized organisms could evolve.
There are many uncertainties
surrounding the origin of
multicellularity. Multicellularity may
have evolved independently for Plants,
Fungi and Animals, or multicellularity
may have evolved only once in
eukaryotes.
The key feature of this cell is that a
multicellular organism is made from a
single cell and the multicellular
organism is not a collection of
independent cells (colonialism). The
main difference between this organism
and single-celled organisms is the way
the cells stay fastened together after
cell division.
Which species was the first
multicellular species is not clear.
Multicellularity is found in all 3 life
cycles (haplontic, diplontic,
haplodiplontic). The 3 main life cycle
types (haplontic, etc.) probably
evolved in single cell species before
multicellularity evolved. If
multicellularity evolved once and is
inherited, perhaps all multicellular
organism descended from a single
haplodiplontic organism.
These multicellular organisms have
undifferentiated cells in the
multicellular stage (all cells in the
haploid or diploid multicellular
organism are made of one kind of cell).
Dinoph
yta, and Fungi are multicellular
Haplontic species.
Most animals are
multicellular Diplontic species.
Most brown
algae and all plants are multicellular
Haplodiplontic species.
The vast majority of multicellular
organisms reproduce only through sex,
although there are exceptions (like
some plants and rotifers) which have
lost the ability to sexually reproduce
or can also reproduce asexually. In
multicellularity, one cell goes on to
produce all the cells in a
multicellular species, so that each
individual organism is genetically
unique. This cell is usually a diploid
zygote, but can be a haploid cell.
This protist is most likely sexual, and
multicellularity evolved only in a
species that reproduces sexually.
Some describe algae multicellularity as
"filamentous".
The first multicellular eukaryuotes are
presumably undifferentiated. For
haplontic these cells are all gametes,
for diplontic these cells are all
capable of meiosis to form gametes, for
haplodiplontic, in the haploid stage
the cells are all gamete producing, in
the diploid stage the cells are all
spore producing.
Some people think that multicellular
organisms arose at least six times: in
animals, fungi and several groups of
algae.
What did the first
multicellular organism look like?
Perhaps it was a haplontic protist that
only did one or more haploid mitoses,
but this time the cells stuck together
(perhaps similar to the way bacteria
form filaments).
An interesting aspect of multicellular
organisms is that oxygen must still
reach each cell for mitochondria to
work, and so this requires that the
cells be only 1 cell thick, or if
thicker have some kind of (circulatory)
system for oxygen to reach each cell.
differentiation evolves.
Multicellular organisms are no longer
all haploid or diploid gamete producing
cells (or spore producing if
haplodiplontic), but are made of gamete
(or spore) producing cells in addition
to somatic cells which copy asexually
through mitosis.
Now, in addition to being large
multicell organisms, multicellular
organisms can have differentiated cells
that form a variety of different shaped
structures, and perform different
functions.
This process will evolve to the
metazoan multicellular differentiation
that arises from a single zygote cell,
where cells have different functions
and shapes.
Differentiation evolves for a
second time in eukaryotes?
this is not the first
monoadmulti one cell leading to a
multicellular organism (attached, free,
interchangible)?
where a multicellular organism is made
from one cell (interchangable, specific
cells: genetic specificity).
It is unknown how multicellular life
stages happen. For example, why one
specific cell line of many produced
from mitosis of a zygote will go on to
do meiosis producing the haploid gamete
cells which will fuse to form the next
zygote, but the many other cells made
from, for example, one of the two cells
made after the zygote divides, will not
contain the line of cells that
ultimately make the gamete producing
cells which continue the life cycle of
the organism. Since presumably each
cell in an organism contains an
identical genome, perhaps a gamete
producing cell can be made from any
cell if specific proteins are present,
or perhaps there is a protein which
simply points to a certain location in
the DNA which is located at a different
location in the DNA for every cell, or
perhaps some other explanation answers
the question of how cell
differentiation can happen when each
cell has the same genome.
A (diploid) zygote cell (the cell made
by two merging gamete cells) now
divides to form all cells in the
differentiated multicellular organism,
and is said to be "totipotent".
Totipotent cells differentiate into
"pluripotent" cells which can make most
but not all cells in the organism.
Pluripotent cells differentiate into
"multipotent" (can make a number of
cells) or "unipotent" cells (can only
make one kind of cell).
plants, this is where the plant kingdom
begins with the evolution of brown
algae (phaeophyta).
ancestor of the "Chromalveolates"
evolving now. Chromalveolates include
the Chromista and Alveolata. The
Chromista include the 3 Phyla
Haptophyta, Cryptophyta (Cryptomonads),
and Heterokontophyta (brown algae
{kelp}, diatoms, water molds).
Alveolata include the 3 Phyla
Dinoflagellata, Apicomplexa (Malaria,
Toxoplasmosis), and Ciliophora
(ciliates).
Chromealveolates have mitochondria
with tubular cristae.
Thomas Cavalier-Smith writes: "The
chromalveolate clade (Cavalier-Smith
1999) and its constituent taxa, kingdom
Chromista (Cavalier-Smith 1981) and
protozoan infrakingdom Alveolata
(Cavalier-Smith 1991b), were all
proposed based on morphological,
biochemical, and evolutionary reasoning
about protein targeting before there
was sequence evidence for any of them.
Now all are strongly supported by such
evidence. Chromalveolates comprise all
algae with chlorophyll c (the
chromophyte algae) and all their
nonphotosynthetic descendants. They
arose by a single symbiogenetic event
in which an early unicellular red alga
was phagocytosed by a biciliate host
and enslaved to provide photosynthate
(Cavalier-Smith 1999, 2002c, 2003a).
The strongest evidence that this
occurred once only in their cenancestor
is the replacement of the red algal
plastid glyceraldehyde phosphate
dehydrogenase (GAPDH) by a duplicate of
the gene for the cytosolic version of
this enzyme in all four chromalveolate
groups with plastids: the alveolate
sporozoa and dinoflagellates and the
chromist cryptomonads and chromobiotes
(Fast et al. 2001). It would be
incredible for such gene duplication,
retargeting by acquiring bipartite
targeting sequences, and loss of the
original red algal gene to have
occurred convergently in four groups,
but it was already pretty incredible
that these groups would all have
evolved a similar protein-targeting
system independently and all happened
to enslave a red alga, evolve
chlorophyll c, and place their plastids
within the rough endoplasmic reticulum
(ER) independently. Yet many assumed
just this because of the false dogma
that symbiogenesis is easy and the
failure of all these groups to cluster
in rRNA trees. For chromobiotes this
retargeting of GAPDH has been
demonstrated only for
heterokonts-information is lacking for
haptophytes. However, there are five
strong synapomorphies for Chromobiota,
making it highly probable that the
group is holophyletic (Cavalier-Smith
1994). They share the presence of the
periplastid reticulum in the
periplastid space instead of a
nucleomorph like cryptomonads, they
uniquely make the carotenoid
fucoxanthin and chlorophyll c3, they
uniquely have a single autofluorescent
cilium, and they have tubular
mitochondrial cristae with an
intracristal filament. Five plastid
genes now extremely robustly support
the monophyly of both chromists and
chromobiotes (Yoon et al. 2002). We are
confident that comparable sequence
evidence from nuclear genes will also
eventually catch up with the general
biological evidence for the holophyly
of chromobiotes to convince even the
most skeptical, who ignore or discount
such valuable evidence that
chromobiotes are holophyletic."
Chromista include phyla:
Heterokontophyta
(heterokonts) (many classes) (includes
colored: golden algae, axodines,
diatoms, yellow-green algea, brown
algae, colorless: water moulds, slime
nets)
Haptophyta
Cryptophyta (cryptomonads) (many
genera)
Alveolates include the phyla:
Dinoflagellata
(Dinoflagellates)
Apicomplexa (Apicomplexans)
Ciliophora (ciliates)
In 1981 Cavalier-Smith created a new
kingdom called "Chromista" in which all
chromalveolates are placed.
There are
a number of classification schemes for
the kingdom Protista and no one system
has emerged as most popular yet.
[1] Fig. 1. A consensus phylogeny of
eukaryotes. The vast majority of
characterized eukaryotes, with the
notable exception of major subgroups of
amoebae, can now be assigned to one of
eight major groups. Opisthokonts (basal
flagellum) have a single basal
flagellum on reproductive cells and
flat mitochondrial cristae (most
eukaryotes have tubular ones).
Eukaryotic photosynthesis originated in
Plants; theirs are the only plastids
with just two outer membranes.
Heterokonts (different flagellae) have
a unique flagellum decorated with
hollow tripartite hairs (stramenopiles)
and, usually, a second plain one.
Cercozoans are amoebae with filose
pseudopodia, often living with in tests
(hard outer shells), some very
elaborate (foraminiferans). Amoebozoa
are mostly naked amoebae (lacking
tests), often with lobose pseudopodia
for at least part of their life cycle.
Alveolates have systems of cortical
alveoli directly beneath their plasma
membranes. Discicristates have discoid
mitochondrial cristae and, in some
cases, a deep (excavated) ventral
feeding groove. Amitochondrial
excavates lack substantial molecular
phylogenetic support, but most have an
excavated ventral feeding groove, and
all lack mitochondria. The tree shown
is based on a consensus of molecular
(1-4) and ultrastructural (16, 17) data
and includes a rough indication of new
ciPCR ''taxa'' (broken black lines)
(7-11). An asterisk preceding the taxon
name indicates probable paraphyletic
group
source: http://www.sciencemag.org/cgi/co
ntent/full/300/5626/1703
[2] Beautiful marine diatoms as seen
through a microscope. These tiny
phytoplankton are encased within a
silicate cell wall. Image ID: corp2365,
NOAA Corps Collection Photographer: Dr.
Neil Sullivan, University of Southern
Calif. NOAA This image is a work of
the National Oceanic and Atmospheric
Administration, taken or made during
the course of an xxxxx? official
duties. As works of the U.S. federal
government, all NOAA images are in the
public domain.
source: http://en.wikipedia.org/wiki/Ima
ge:Diatoms_through_the_microscope.jpg
ancestor of Chromalveolate Phlyum
Haptophyta evolving now.
Some Haptophytes
are haplodiploid (alternate between
haploid and diploid cycles that both
have mitosis), and this group is the
most primitive with a haplodiploid life
cycle.
Haptophytes are single cellular.
Haptophytes are found only in all
oceans (marine) and are flagellates,
almost all with plastids with
chlorophylls a and c, with two flagella
and one additional locomotor/feeding
organelle, the haptonema.
Haptophyta are a group of algae
(phytoplankton).
The chloroplasts are pigmented
similarly to those of the heterokonts,
such as golden algae, but the structure
of the rest of the cell is different,
so it may be that they are a separate
line whose chloroplasts are derived
from similar endosymbionts.
The cells typically have
two slightly unequal flagella, both of
which are smooth, and a unique
organelle called a haptonema, which is
superficially similar to a flagellum
but differs in the arrangement of
microtubules and in its use.
Haptophytes
have tubular mitochondria cristae.
Most
haptophytes are coccolithophores, which
live strictly in the oceans (marine)
and are ornmmented with calcified
scales called coccoliths, which are
sometimes found as microfossils. Other
planktonic haptophytes of note include
Chrysochromulina and Prymnesium, which
periodically form toxic marine algal
blooms. Both molecular and
morphological evidence supports their
division into five orders.
Emiliania is a small organism that is
famous for turning huge portions of the
ocean bright turquoise during its
blooms. They are also known for
contributing to the white cliffs of
Dover because of the calcite in their
coccolith cell structure. They play a
very important role in the carbon cycle
in the ocean because they form calcium
carbonate exoskeletons that sink to the
bottom of the ocean floor when they
die. They are also one of the worlds
major calcite producers.
Sexual reproduction: Asexual, Open
mitosis with spindle nucleating
(originating?) in cytoplasm.
Phaeocystis colonial
cells diploid, motile cells haploid or
diploid; reproduction by vegetative
division of non-motile cells and
fragmentation of colonies, vegetative
division of motile cells, or by fusion
of gametes.
Members of the Haptophytes Genus
"Phaocystis" form colonies (see
photo).
Haptophytes are also called
"Prymnesiophytes"
Some Haptophyta have hard shell made of
calcium carbonate evolves around the
single-celled species living in the
ocean.
KINGDOM Protista (Chromalveolata)
PHYLUM Haptophyta
CLASS
Pavlovophyceae
ORDER Pavlovales
CLASS Prymnesiophyceae
ORDER Prymnesiales
ORDER Phaeocystales
ORDER
Isochrysidales
ORDER Coccolithales
[1] Fig. 1. A consensus phylogeny of
eukaryotes. The vast majority of
characterized eukaryotes, with the
notable exception of major subgroups of
amoebae, can now be assigned to one of
eight major groups. Opisthokonts (basal
flagellum) have a single basal
flagellum on reproductive cells and
flat mitochondrial cristae (most
eukaryotes have tubular ones).
Eukaryotic photosynthesis originated in
Plants; theirs are the only plastids
with just two outer membranes.
Heterokonts (different flagellae) have
a unique flagellum decorated with
hollow tripartite hairs (stramenopiles)
and, usually, a second plain one.
Cercozoans are amoebae with filose
pseudopodia, often living with in tests
(hard outer shells), some very
elaborate (foraminiferans). Amoebozoa
are mostly naked amoebae (lacking
tests), often with lobose pseudopodia
for at least part of their life cycle.
Alveolates have systems of cortical
alveoli directly beneath their plasma
membranes. Discicristates have discoid
mitochondrial cristae and, in some
cases, a deep (excavated) ventral
feeding groove. Amitochondrial
excavates lack substantial molecular
phylogenetic support, but most have an
excavated ventral feeding groove, and
all lack mitochondria. The tree shown
is based on a consensus of molecular
(1-4) and ultrastructural (16, 17) data
and includes a rough indication of new
ciPCR ''taxa'' (broken black lines)
(7-11). An asterisk preceding the taxon
name indicates probable paraphyletic
group
source: http://www.sciencemag.org/cgi/co
ntent/full/300/5626/1703
[2] Emiliania huxleyi, a
coccolithophore. Photo courtesy Dr.
Markus Geisen - photographer, and The
Natural History Museum. PD
source: http://en.wikipedia.org/wiki/Ima
ge:Emiliania_huxleyi_3.jpg
ancestor of the Chromalveolate Phylum
"Cryptophyta" (Cryptomonads) evolving
now.
The cryptomonads are a small group of
flagellates, most of which have
chloroplasts. They are common in
freshwater, and also occur in marine
and brackish habitats. Each cell has an
anterior groove or pocket with
typically two slightly unequal flagella
at the edge of the pocket.
Cryptomonads
distinguished by the presence of
characteristic extrusomes called
ejectisomes, which consist of two
connected spiral ribbons held under
tension. If the cells are irritated
either by mechanical, chemical or light
stress, they discharge, propelling the
cell in a zig-zag course away from the
disturbance. Large ejectisomes, visible
under the light microscope, are
associated with the pocket; smaller
ones occur elsewhere on the cell.
Crypto
monads have one or two chloroplasts,
except for Chilomonas which has
leucoplasts and Goniomonas which lacks
plastids entirely. These contain
chlorophylls a and c, together with
phycobilins and other pigments, and
vary in color from brown to green. Each
is surrounded by four membranes, and
there is a reduced cell nucleus called
a nucleomorph between the middle two.
This indicates that the chloroplast was
derived from a eukaryotic symbiont,
shown by genetic studies to have been a
red alga.
A few cryptomonads, such as
Cryptomonas, can form palmelloid
stages, but readily escape the
surrounding mucus to become free-living
flagellates again. Cryptomonad flagella
are inserted parallel to one another,
and are covered by bipartite hairs
called mastigonemes, formed within the
endoplasmic reticulum and transported
to the cell surface. Small scales may
also be present on the flagella and
cell body. The mitochondria have flat
cristae, and mitosis is open; sexual
reproduction has also been reported.
Originally the cryptomonads were
considered close relatives of the
dinoflagellates because of their
similar pigmentation. Later botanists
treated them as a separate division,
Cryptophyta, while zoologists treated
them as the flagellate order
Cryptomonadida. There is considerable
evidence that cryptomonad chloroplasts
are closely related to those of the
heterokonts and haptophytes, and the
three groups are sometimes united as
the Chromista. However, the case that
the organisms themselves are related is
not very strong, and they may have
acquired chloroplasts independently.
Crytomonads often forms blooms in
greater depths of lakes, or during
winter beneath the ice. The cells are
usually brownish in color, and have a
slit-like furrow at the anterior. They
are not known to produce any toxins and
are used to feed small zooplankton,
which is the food source for small fish
in fish farming.
Reproduction:
Number of species:
Size and shape: 10-50 μm
in size and flattened in shape
Mitochondria
Christae: flat (which is unusual, as
most chromalveolates have tubular
christae). Cryotphyta may be more
closely related to the Plant Kingdom
and nearest Glaucophyta which also have
flat christae.
After one species of jakobid that
changes tubular to flat christae,
cryptophyta are the most ancient phylum
to have flat christae.
KINGDOM
Protista (Chromalveolata)
PHYLUM Cryptophyta
CLASS
Cryptomonadea
ORDER Pyrenomonadales Novarino &
Lucas, 1993
ORDER Cryptomonadales
Pascher, 1913
[1] Fig. 1. A consensus phylogeny of
eukaryotes. The vast majority of
characterized eukaryotes, with the
notable exception of major subgroups of
amoebae, can now be assigned to one of
eight major groups. Opisthokonts (basal
flagellum) have a single basal
flagellum on reproductive cells and
flat mitochondrial cristae (most
eukaryotes have tubular ones).
Eukaryotic photosynthesis originated in
Plants; theirs are the only plastids
with just two outer membranes.
Heterokonts (different flagellae) have
a unique flagellum decorated with
hollow tripartite hairs (stramenopiles)
and, usually, a second plain one.
Cercozoans are amoebae with filose
pseudopodia, often living with in tests
(hard outer shells), some very
elaborate (foraminiferans). Amoebozoa
are mostly naked amoebae (lacking
tests), often with lobose pseudopodia
for at least part of their life cycle.
Alveolates have systems of cortical
alveoli directly beneath their plasma
membranes. Discicristates have discoid
mitochondrial cristae and, in some
cases, a deep (excavated) ventral
feeding groove. Amitochondrial
excavates lack substantial molecular
phylogenetic support, but most have an
excavated ventral feeding groove, and
all lack mitochondria. The tree shown
is based on a consensus of molecular
(1-4) and ultrastructural (16, 17) data
and includes a rough indication of new
ciPCR ''taxa'' (broken black lines)
(7-11). An asterisk preceding the taxon
name indicates probable paraphyletic
group COPYRIGHTED
source: http://www.sciencemag.org/cgi/co
ntent/full/300/5626/1703
[2] Figure 1. Phylogenetic hypothesis
of the eukaryotic lineage based on
ultrastructural and molecular data.
Organisms are divided into three main
groups distinguished by mitochondrial
cristal shape (either discoidal,
flattened or tubular). Unbroken lines
indicate phylogenetic relationships
that are firmly supported by available
data; broken lines indicate
uncertainties in phylogenetic
placement, resolution of which will
require additional data. Color coding
of organismal genus names indicates
mitochondrial genomes that have been
completely (Table 1), almost completely
(Jakoba, Naegleria and
Thraustochytrium) or partially (*)
sequenced by the OGMP (red), the FMGP
(black) or other groups (green). Names
in blue indicate those species whose
mtDNAs are currently being sequenced by
the OGMP or are future candidates for
complete sequencing. Amitochondriate
retortamonads are positioned at the
base of the tree, with broken arrows
denoting the endosymbiotic origin(s) of
mitochondria from a Rickettsia-like
eubacterium. Macrophar.,
Macropharyngomonas. COPYRIGHTED
source: http://nar.oxfordjournals.org/cg
i/content/full/26/4/865
ancestor of the Chromalveolate Phylum
"Heterokontophyta" (Heterokonts also
called Stramenopiles) evolving now.
Heterokonts include brown algae,
diatoms, golden algae, axodines,
yellow-green algae, water moulds and
slime nets.
Heterkonts evolved very near the
same time as the Euglinozoa did.
Heterokonts
all have mitochondria with tubular
christae. The motile cells of
heterokonts all have two unequal cilia
(flagella), one "tinsel" (covered with
hairs {mastigonemes}) cilium and one
"whiplash" (free of hair) cilium.
KINGDOM
Protista (Chromalveolata)
PHYLUM Heterokontophyta
Colored groups
CLASS
Chrysophyceae (golden algae)
CLASS
Synurophyceae
CLASS Actinochrysophyceae
(axodines)
CLASS Pelagophyceae
CLASS
Phaeothamniophyceae
CLASS Bacillariophyceae (diatoms)
CLASS
Raphidophyceae
CLASS Eustigmatophyceae
CLASS Xanthophyceae
(yellow-green algae)
CLASS Phaeophyceae
(brown algae)
Colorless groups
CLASS
Oomycetes(water moulds)
CLASS
Hypochytridiomycetes
CLASS Bicosoecea
CLASS
Labyrinthulomycetes(slime nets)
CLASS
Opalinea
CLASS Proteromonadea
[1] Fig. 1. A consensus phylogeny of
eukaryotes. The vast majority of
characterized eukaryotes, with the
notable exception of major subgroups of
amoebae, can now be assigned to one of
eight major groups. Opisthokonts (basal
flagellum) have a single basal
flagellum on reproductive cells and
flat mitochondrial cristae (most
eukaryotes have tubular ones).
Eukaryotic photosynthesis originated in
Plants; theirs are the only plastids
with just two outer membranes.
Heterokonts (different flagellae) have
a unique flagellum decorated with
hollow tripartite hairs (stramenopiles)
and, usually, a second plain one.
Cercozoans are amoebae with filose
pseudopodia, often living with in tests
(hard outer shells), some very
elaborate (foraminiferans). Amoebozoa
are mostly naked amoebae (lacking
tests), often with lobose pseudopodia
for at least part of their life cycle.
Alveolates have systems of cortical
alveoli directly beneath their plasma
membranes. Discicristates have discoid
mitochondrial cristae and, in some
cases, a deep (excavated) ventral
feeding groove. Amitochondrial
excavates lack substantial molecular
phylogenetic support, but most have an
excavated ventral feeding groove, and
all lack mitochondria. The tree shown
is based on a consensus of molecular
(1-4) and ultrastructural (16, 17) data
and includes a rough indication of new
ciPCR ''taxa'' (broken black lines)
(7-11). An asterisk preceding the taxon
name indicates probable paraphyletic
group COPYRIGHTED
source: http://www.sciencemag.org/cgi/co
ntent/full/300/5626/1703
[2] Figure 1. Phylogenetic hypothesis
of the eukaryotic lineage based on
ultrastructural and molecular data.
Organisms are divided into three main
groups distinguished by mitochondrial
cristal shape (either discoidal,
flattened or tubular). Unbroken lines
indicate phylogenetic relationships
that are firmly supported by available
data; broken lines indicate
uncertainties in phylogenetic
placement, resolution of which will
require additional data. Color coding
of organismal genus names indicates
mitochondrial genomes that have been
completely (Table 1), almost completely
(Jakoba, Naegleria and
Thraustochytrium) or partially (*)
sequenced by the OGMP (red), the FMGP
(black) or other groups (green). Names
in blue indicate those species whose
mtDNAs are currently being sequenced by
the OGMP or are future candidates for
complete sequencing. Amitochondriate
retortamonads are positioned at the
base of the tree, with broken arrows
denoting the endosymbiotic origin(s) of
mitochondria from a Rickettsia-like
eubacterium. Macrophar.,
Macropharyngomonas. COPYRIGHTED
source: http://nar.oxfordjournals.org/cg
i/content/full/26/4/865
Algae (Phaeophyta) evolves now.
Brown Algae is the most genetically
ancient multicellular organism still
living on earth. In addition to being
first to evolve multicellularity, cell
differentiation (cells of different
types) is already present in all brown
algae.
Genetic comparison shows the ancestor
of the Chromalveolate Heterokont Brown
Algae (Phaeophyta) evolving now.
Brown Algae is the most genetically
ancient multicellular organism still
living on earth. In addition to being
first to evolve multicellularity, cell
differentiation (cells of different
types) is already present in all brown
algae.
Brown algae belong to a large group
called the heterokonts, most of which
are colored flagellates. Most contain
the pigment fucoxanthin, which is
responsible for the distinctive
greenish-brown color that gives brown
algae their name. Brown algae are
unique among heterokonts in developing
into multicellular forms with
differentiated tissues, but they
reproduce by means of flagellate
spores, which closely resemble other
heterokont cells. Genetic studies show
their closest relatives are the
yellow-green algae.
Most Brown algae are haplodiplontic.
KINGDOM Protista
(Chromalveolata)
PHYLUM Heterokontophyta
Colored groups
CLASS Phaeophyceae
(brown algae)
Some people view brown algae as being
in the plant kingdom, and others as
being a multicellular protist in the
protist kingdom.
2. Brown algae range from small
forms with simple filaments to large
multicellular (50-100 m long) seaweeds.
(Fig. 30.8)
3. Brown algae have
chlorophylls a and c and a fucoxanthin
that give them their color.
4. Their
reserve food is a carbohydrate called
laminarin.
5. Seaweed refers to any large,
complex alga.
6. Their cell walls
contain a mucilaginous water-retaining
material that inhibits desiccation.
7.
Laminaria is an intertidal kelp that is
unique among protists; this genus shows
tissue differentiation.
8. Nereocystis and
Macrocystis are giant kelps found in
deeper water anchored to the bottom by
their holdfasts.
9. Individuals of the
genus Sargassum sometimes break off
from their holdfasts and form floating
masses.
10. Brown algae provide food
and habitat for marine organisms, and
they are also important to humans.
a. Brown algae are harvested for human
food and for fertilizer in several
parts of the world.
b. They are a
source of algin, a pectin-like
substance added to give foods a stable,
smooth consistency.
11. Most have an
alternation of generations life cycle.
12. Fucus is an intertidal rockweed;
meiotic cell division produces gametes
and adult is always diploid.
[1] Fig. 1. A consensus phylogeny of
eukaryotes. The vast majority of
characterized eukaryotes, with the
notable exception of major subgroups of
amoebae, can now be assigned to one of
eight major groups. Opisthokonts (basal
flagellum) have a single basal
flagellum on reproductive cells and
flat mitochondrial cristae (most
eukaryotes have tubular ones).
Eukaryotic photosynthesis originated in
Plants; theirs are the only plastids
with just two outer membranes.
Heterokonts (different flagellae) have
a unique flagellum decorated with
hollow tripartite hairs (stramenopiles)
and, usually, a second plain one.
Cercozoans are amoebae with filose
pseudopodia, often living with in tests
(hard outer shells), some very
elaborate (foraminiferans). Amoebozoa
are mostly naked amoebae (lacking
tests), often with lobose pseudopodia
for at least part of their life cycle.
Alveolates have systems of cortical
alveoli directly beneath their plasma
membranes. Discicristates have discoid
mitochondrial cristae and, in some
cases, a deep (excavated) ventral
feeding groove. Amitochondrial
excavates lack substantial molecular
phylogenetic support, but most have an
excavated ventral feeding groove, and
all lack mitochondria. The tree shown
is based on a consensus of molecular
(1-4) and ultrastructural (16, 17) data
and includes a rough indication of new
ciPCR ''taxa'' (broken black lines)
(7-11). An asterisk preceding the taxon
name indicates probable paraphyletic
group COPYRIGHTED
source: http://www.sciencemag.org/cgi/co
ntent/full/300/5626/1703
[2] Figure 1. Phylogenetic hypothesis
of the eukaryotic lineage based on
ultrastructural and molecular data.
Organisms are divided into three main
groups distinguished by mitochondrial
cristal shape (either discoidal,
flattened or tubular). Unbroken lines
indicate phylogenetic relationships
that are firmly supported by available
data; broken lines indicate
uncertainties in phylogenetic
placement, resolution of which will
require additional data. Color coding
of organismal genus names indicates
mitochondrial genomes that have been
completely (Table 1), almost completely
(Jakoba, Naegleria and
Thraustochytrium) or partially (*)
sequenced by the OGMP (red), the FMGP
(black) or other groups (green). Names
in blue indicate those species whose
mtDNAs are currently being sequenced by
the OGMP or are future candidates for
complete sequencing. Amitochondriate
retortamonads are positioned at the
base of the tree, with broken arrows
denoting the endosymbiotic origin(s) of
mitochondria from a Rickettsia-like
eubacterium. Macrophar.,
Macropharyngomonas. COPYRIGHTED
source: http://nar.oxfordjournals.org/cg
i/content/full/26/4/865
evolve.
Genetic comparison shows the ancestor
of the Chromalveolate Heterokont
Diatoms evolving now.
Diatoms are diplontic.
Diatoms are a very common types of
phytoplankton. Most diatoms are
unicellular, although some form chains
or simple colonies. A characteristic
feature of diatom cells is that they
are encased within a unique cell wall
made of silica. These walls show a wide
diversity in form, some quite beautiful
and ornate, but usually consist of two
symmetrical sides with a split between
them, hence the group name.
Life Cycle
When a cell divides each new cell
takes as its epitheca a valve of the
parent frustule, and within ten to
twenty minutes builds its own
hypotheca; this process may occur
between one and eight times per day.
Availability of dissolved silica limits
the rate of vegetative reproduction,
but also because this method
progressively reduces the average size
of the diatom frustule in a given
population there is a certain threshold
at which restoration of frustule size
is neccesary. Auxospores are then
produced, which are cells that posses a
different wall structure lacking the
siliceous frustule and swell to the
maximum frustule size. The auxospore
then forms an initial cell which forms
a new frustule of maximum size within
itself.
KINGDOM Protista
(Chromalveolata)
PHYLUM Heterokontophyta
Colored groups
CLASS
Bacillariophyceae (diatoms)
There are more than 200 genera of
living diatoms, and it is estimated
that there are approximately 100 000
extant species (Round & Crawford,
1990). Diatoms are a widespread group
and can be found in the oceans, in
freshwater, in soils and on damp
surfaces.
Their chloroplasts are typical of
heterokonts, with four membranes and
containing pigments such as
fucoxanthin. Individuals usually lack
flagella, but they are present in
gametes and have the usual heterokont
structure, except they lack the hairs
(mastigonemes) characteristic in other
groups.
Most diatom species are non-motile but
some are capable of an oozing motion.
As their relatively dense cell walls
cause them to readily sink, planktonic
forms in open water usually rely on
turbulent mixing of the upper layers by
the wind to keep them suspended in
sunlit surface waters. Some species
actively regulate their buoyancy to
counter sinking.
Diatoms cells are contained within a
unique silicate (silicic acid) cell
wall comprised of two separate valves
(or shells). The biogenic silica that
the cell wall is composed of is
synthesised intracellularly by the
polymerisation of silicic acid
monomers. This material is then
extruded to the cell exterior and added
to the wall. Diatom cell walls are also
called frustules or tests, and their
two valves typically overlap one other
like the two halves of a petri dish. In
most species, when a diatom divides to
produce two daughter cells, each cell
keeps one of the two valves and grows a
smaller valve within it. As a result,
after each division cycle the average
size of diatom cells in the population
gets smaller. Once such cells reach a
certain minimum size, rather than
simply divide vegetatively, they
reverse this decline by forming an
auxospore. This expands in size to give
rise to a much larger cell, which then
returns to size-diminishing divisions.
Auxospore production is almost always
linked to meiosis and sexual
reproduction.
Diatoms are traditionally divided into
two orders: centric diatoms
(Centrales), which are radially
symmetric, and pennate diatoms
(Pennales), which are bilaterally
symmetric. The former are paraphyletic
to the latter. A more recent
classification is that of Round &
Crawford (1990), who divide the diatoms
into three classes: centric diatoms
(Coscinodiscophyceae), pennate diatoms
without a raphe (Fragilariophyceae),
and pennate diatoms with a raphe
(Bacillariophyceae). It is probable
there will be further revisions as our
understanding of their relationships
increases.
Planktonic forms in freshwater and
marine environments typically exhibit a
"bloom and bust" lifestyle. When
conditions in the upper mixed layer
(nutrients and light) are favourable
(e.g. at the start of spring) their
competitive edge (Furnas, 1990) allows
them to quickly dominate phytoplankton
communities ("bloom").
When conditions turn unfavourable,
usually upon depletion of nutrients,
diatom cells typically increase in
sinking rate and exit the upper mixed
layer ("bust"). This sinking is induced
by either a loss of buoyancy control,
the synthesis of mucilage that sticks
diatoms cells together, or the
production of heavy resting spores.
In the open ocean, the condition that
typically causes diatom (spring) blooms
to end is a lack of silicon. Unlike
other nutrients, this is only a major
requirement of diatoms so it is not
regenerated in the plankton ecosystem
as efficiently as, for instance,
nitrogen or phosphorus nutrients. This
can be seen in maps of surface nutrient
concentrations - as nutrients decline
along gradients, silicon is usually the
first to be exhausted (followed
normally by nitrogen then phosphorus).
Heterokont chloroplasts appear to be
derived from those of red algae, rather
than directly from prokaryotes as
occurs in plants. This suggests they
had a more recent origin than many
other algae. However, fossil evidence
is scant, and it is really only with
the evolution of the diatoms themselves
that the heterokonts make a serious
impression on the fossil record.
The earliest known fossil diatoms date
from the early Jurassic (~185 Ma;
Kooistra & Medlin, 1996), although
recent genetic (Kooistra & Medlin,
1996) and sedimentary (Schieber,
Krinsley & Riciputi, 2000) evidence
suggests an earlier origin. Medlin et
al. (1997) suggest that their origin
may be related to the end-Permian mass
extinction (~250 Ma), after which many
marine niches were opened. The gap
between this event and the time that
fossil diatoms first appear may
indicate a period when diatoms were
unsilicified and their evolution was
cryptic (Raven & Waite, 2004). Since
the advent of silicification, diatoms
have made a significant impression on
the fossil record, with major deposits
of fossil diatoms found as far back as
the early Cretaceous, and some rocks
(diatomaceous earth, diatomite,
kieselguhr) being composed almost
entirely of them.
Although the diatoms
may have existed since the Triassic,
the timing of their ascendancy and
"take-over" of the silicon cycle is
more recent.
3. Diatoms are the most numerous
unicellular algae in the oceans. (Fig.
30.6a)
4. They are extremely numerous
and an important source of food and O2
in aquatic systems.
5. Diatom cell walls
consist of two silica-impregnated
halves or valves.
a. When diatoms
reproduce asexually, each received one
old valve.
b. The new valve fits
inside the old one; therefore, the new
diatom is smaller than the original
one.
c. This continues until
they are about 30 percent of their
original size.
d. Then they
reproduce sexually; a zygote grows and
divides mitotically to form diatoms of
normal size.
6. The cell wall has an
outer layer of silica (glass) with a
variety of markings formed by pores.
7. Diatom remains accumulate on the
ocean floor and are mined as
diatomaceous earth for use as filters,
abrasives, etc.
Life Cycle (cont.)
Many neritic planktonic
diatoms alternate between a vegetative
reproductive phase and a thicker walled
resting cyst or statospore stage. The
siliceous resting spore commonly forms
after a period of active vegetative
reproduction when nutrient levels have
been depleted. Statospores may remain
entirely within the the parent cell,
partially within the parent cell or be
isolated from it. An increase in
nutreint levels and/or length of
daylight cause the statospore to
germinate and return to its normal
vegatative state. Seasonal upwelling is
therefore a vital part of many diatoms
life cycle as a provider of nutrients
and as a transport mechanism which
brings statospores or their vegetative
products up into the photic zone.
The resting
spore morphology of some species is
similar to that of the corresponding
vegetative cell, whereas in other
species the resting spores and the
vegetative cells differ strongly. The
two valves of a resting spore may be
similar or distinctly different. Often
the first valve formed is more similar
to the valves of the vegetative cells
than the second valve.
[1] Fig. 1. A consensus phylogeny of
eukaryotes. The vast majority of
characterized eukaryotes, with the
notable exception of major subgroups of
amoebae, can now be assigned to one of
eight major groups. Opisthokonts (basal
flagellum) have a single basal
flagellum on reproductive cells and
flat mitochondrial cristae (most
eukaryotes have tubular ones).
Eukaryotic photosynthesis originated in
Plants; theirs are the only plastids
with just two outer membranes.
Heterokonts (different flagellae) have
a unique flagellum decorated with
hollow tripartite hairs (stramenopiles)
and, usually, a second plain one.
Cercozoans are amoebae with filose
pseudopodia, often living with in tests
(hard outer shells), some very
elaborate (foraminiferans). Amoebozoa
are mostly naked amoebae (lacking
tests), often with lobose pseudopodia
for at least part of their life cycle.
Alveolates have systems of cortical
alveoli directly beneath their plasma
membranes. Discicristates have discoid
mitochondrial cristae and, in some
cases, a deep (excavated) ventral
feeding groove. Amitochondrial
excavates lack substantial molecular
phylogenetic support, but most have an
excavated ventral feeding groove, and
all lack mitochondria. The tree shown
is based on a consensus of molecular
(1-4) and ultrastructural (16, 17) data
and includes a rough indication of new
ciPCR ''taxa'' (broken black lines)
(7-11). An asterisk preceding the taxon
name indicates probable paraphyletic
group COPYRIGHTED
source: http://www.sciencemag.org/cgi/co
ntent/full/300/5626/1703
[2] Figure 1. Phylogenetic hypothesis
of the eukaryotic lineage based on
ultrastructural and molecular data.
Organisms are divided into three main
groups distinguished by mitochondrial
cristal shape (either discoidal,
flattened or tubular). Unbroken lines
indicate phylogenetic relationships
that are firmly supported by available
data; broken lines indicate
uncertainties in phylogenetic
placement, resolution of which will
require additional data. Color coding
of organismal genus names indicates
mitochondrial genomes that have been
completely (Table 1), almost completely
(Jakoba, Naegleria and
Thraustochytrium) or partially (*)
sequenced by the OGMP (red), the FMGP
(black) or other groups (green). Names
in blue indicate those species whose
mtDNAs are currently being sequenced by
the OGMP or are future candidates for
complete sequencing. Amitochondriate
retortamonads are positioned at the
base of the tree, with broken arrows
denoting the endosymbiotic origin(s) of
mitochondria from a Rickettsia-like
eubacterium. Macrophar.,
Macropharyngomonas. COPYRIGHTED
source: http://nar.oxfordjournals.org/cg
i/content/full/26/4/865
molds (Oomycetes OemISETEZ) evolve.
Genetic
comparison shows the ancestor of the
Chromalveolate Heterokont Water molds
(Oomycetes OemISETEZ) evolving now.
Oomycetes (Water molds), with about 580
species, vary from unicellular, to
multicellular highly brached
filamentous forms. The filamentous
form is called "coenocytic" (grows as a
large multinucleate cell that results
from multiple nuclear divisions without
cell divisions, also called "mycelium"
in fungi) Oomycetes grow by closed
(or nearly closed) mitosis with pairs
of centrioles near the poles .
Filamentous forms grow by mitosis, but
only the nucleus is duplicated
(karyokinesis), no septa (horizontal
cell wall) is constructed, making these
multinucleate very large single cells.
Technically, filamentous oomycetes are
3 celled multicellular organisms
because a septa forms between the
vegetative filament and the diploid
sporangium (and oogonium) cells (and
the haploid antheridium multinucleate
cells are not free swimming), but many
people label oomycetes as single celled
organism. But it appears clear that
oomycetes would be constructed of many
cells if a cell wall was built at
mitosis. Sexual forms are diploid and
reproduce by conjugation.
Water Molds are microscopic organisms
that reproduce both sexually and
asexually and are composed of mycelia,
or a tube-like vegetative body (all of
an organism's mycelia are called its
thallus). The name "water mould" refers
to the fact that they thrive under
conditions of high humidity and running
surface water.
Water molds were originally classified
as fungi, but are now known to have
developed separately and show a number
of differences. Their cell walls are
composed of cellulose rather than
chitin and lack septa (a wall that
divides two spaces) except where
reproductive cells are produced, in
addition to having gene sequences more
closely related to brown algae than
fungi. Also, in the vegetative state
they have diploid nuclei, whereas fungi
have haploid nuclei.
The oomycetes include the water molds,
white rusts and the downy mildews. Many
oomycetes are multinucleate filaments
(hyphae) that resemble fungi. These
hyphae have no cross walls, but are one
long hollow tube and are called
"coenocytic". They were once thought to
be related to the fungi, but their cell
walls are made of cellulose, not chitin
as they are in the true fungi. The
superficial resemblance of the fungi
and the oomycetes is likely a case of
convergent evolution. Both groups have
a filamentous (hyphal) body form with a
high surface area to volume ration
which facilitates uptake of nutrients
from their surroundings.
The oomycetes are saprobic and
parasitic forms, including water molds
like Saprolegnia and downey mildews
like Peronospora.
1. These organisms (and slime
molds) resemble fungi but all have
flagellated cells which fungi never
do.
2. Water molds possess a cell
wall but it is made of cellulose, not
chitin as in fungi.
3. Water molds
produce diploid (2n) zoospores and
meiosis produces the gametes.
2. Aquatic water molds
parasitize fishes, forming furry
growths on their gills, and decompose
remains.
3. Terrestrial water molds
parasitize insects and plants; a water
mold caused the 1840s Irish potato
famine.
4. Water molds have a
filamentous body but cell walls are
composed largely of cellulose.
5. During
asexual reproduction, they produce
diploid motile spores (2n zoospores)
with flagella.
6. Unlike fungi, the adult
is diploid; gametes are produced by
meiosis.
7. Eggs are produced in
enlarged oogonia.
KINGDOM Protista
(Chromalveolata)
PHYLUM Heterokontophyta
Colorless groups
CLASS Oomycetes
(water moulds)
Oomycetes have mitochondria with
tubular christae.
Water mould motile cells are produced
as asexual spores called zoospores,
which capitalize on surface water
(including precipitation on plant
surfaces) for movement. The Zoospores
have 2 unequal anterior (apical)
flagella. They also produce sexual
spores, called oospores, that are
translucent double-walled spherical
structures used to survive adverse
environmental conditions.
The water molds are among the most
important plant pathogenic (capable of
causing disease) organisms that may be
facultatively or obligately parasitic.
The majority can be divided into three
groups, although more exist.
* The Phytophthora group is a genus
that causes diseases such as dieback,
potato blight (caused the potato famine
in Ireland), sudden oak death and
rhododendron root rot.
* The Pythium group is a genus that
is more ubiquitous than Phytophythora
and individual species have larger host
ranges, usually causing less damage.
Pythium damping off is a very common
problem in greenhouses where the
organism kills newly emerged seedlings.
Mycoparasitic members of this group
(e.g. P. oligandrum) parasitise other
oomycetes and fungi and have been
employed as biocontrol agents . One
Pythium species, Pythium insidiosum is
also known to infect mammals.
* The third group are the downy
mildews, which are easily identifable
by the appearance of white "mildew" on
leaf surfaces (although this group can
be confused with the unrelated powdery
mildews).
A male nuclei from a multinucleate
haploid cell is transfered to into the
haploid egg cell; the male gamete is
not free moving, only the female
gametes are although contained within
the oogonium.
[1] Fig. 1. A consensus phylogeny of
eukaryotes. The vast majority of
characterized eukaryotes, with the
notable exception of major subgroups of
amoebae, can now be assigned to one of
eight major groups. Opisthokonts (basal
flagellum) have a single basal
flagellum on reproductive cells and
flat mitochondrial cristae (most
eukaryotes have tubular ones).
Eukaryotic photosynthesis originated in
Plants; theirs are the only plastids
with just two outer membranes.
Heterokonts (different flagellae) have
a unique flagellum decorated with
hollow tripartite hairs (stramenopiles)
and, usually, a second plain one.
Cercozoans are amoebae with filose
pseudopodia, often living with in tests
(hard outer shells), some very
elaborate (foraminiferans). Amoebozoa
are mostly naked amoebae (lacking
tests), often with lobose pseudopodia
for at least part of their life cycle.
Alveolates have systems of cortical
alveoli directly beneath their plasma
membranes. Discicristates have discoid
mitochondrial cristae and, in some
cases, a deep (excavated) ventral
feeding groove. Amitochondrial
excavates lack substantial molecular
phylogenetic support, but most have an
excavated ventral feeding groove, and
all lack mitochondria. The tree shown
is based on a consensus of molecular
(1-4) and ultrastructural (16, 17) data
and includes a rough indication of new
ciPCR ''taxa'' (broken black lines)
(7-11). An asterisk preceding the taxon
name indicates probable paraphyletic
group COPYRIGHTED
source: http://www.sciencemag.org/cgi/co
ntent/full/300/5626/1703
[2] Figure 1. Phylogenetic hypothesis
of the eukaryotic lineage based on
ultrastructural and molecular data.
Organisms are divided into three main
groups distinguished by mitochondrial
cristal shape (either discoidal,
flattened or tubular). Unbroken lines
indicate phylogenetic relationships
that are firmly supported by available
data; broken lines indicate
uncertainties in phylogenetic
placement, resolution of which will
require additional data. Color coding
of organismal genus names indicates
mitochondrial genomes that have been
completely (Table 1), almost completely
(Jakoba, Naegleria and
Thraustochytrium) or partially (*)
sequenced by the OGMP (red), the FMGP
(black) or other groups (green). Names
in blue indicate those species whose
mtDNAs are currently being sequenced by
the OGMP or are future candidates for
complete sequencing. Amitochondriate
retortamonads are positioned at the
base of the tree, with broken arrows
denoting the endosymbiotic origin(s) of
mitochondria from a Rickettsia-like
eubacterium. Macrophar.,
Macropharyngomonas. COPYRIGHTED
source: http://nar.oxfordjournals.org/cg
i/content/full/26/4/865
(Ciliates, Dinoflagellates,
Apicomplexans) evolve.
Genetic comparison
shows the ancestor of the
Chromalveolate Alveolata (Ciliates,
Dinoflagellates, Apicomplexans)
evolving now.
The alveolates are a major line of
protists. There are three main groups,
which are very divergent in form, but
are now known to be close relatives
based on various ultrastructural and
genetic similarities:
Ciliates Very common protozoa,
with many short cilia arranged in rows
Apicom
plexa Parasitic protozoa that lack
locomotive structures except in
gametes
Dinoflagellates Mostly marine
flagellates, many of which have
chloroplasts
The most notable shared characteristic
is the presence of cortical alveoli,
flattened vesicles packed into a
continuous layer supporting the
membrane, typically forming a flexible
pellicle. In dinoflagellates they often
form armor plates. Alveolates have
mitochondria with tubular cristae, and
their flagella or cilia have a distinct
structure.
The Apicomplexa and dinoflagellates may
be more closely related to each other
than to the ciliates. Both have
plastids, and most share a bundle or
cone of microtubules at the top of the
cell. In apicomplexans this forms part
of a complex used to enter host cells,
while in some colorless dinoflagellates
it forms a peduncle used to ingest
prey.
DOMAIN Eukaryota - eukaryotes
KINGDOM
Protozoa (Goldfuss, 1818) R. Owen, 1858
- protozoa
SUBKINGDOM Biciliata
INFRAKINGDOM
Alveolata Cavalier-Smith, 1991
PHYLUM Myzozoa Cavalier-Smith & Chao,
2004
PHYLUM Ciliophora (Doflein,
1901) Copeland, 1956 - ciliates
Relationships between some of these the
major groups were suggested during the
1980s, and between all three by
Cavalier-Smith, who introduced the
formal name Alveolata in 1991. They
were confirmed by a genetic study by
Gajadhar et al. Some studies suggested
the haplosporids, mostly parasites of
marine invertebrates, might belong here
but they lack alveoli and are now
placed among the Cercozoa.
The development of plastids among the
alveolates is uncertain. Cavalier-Smith
proposed the alveolates developed from
a chloroplast-containing ancestor,
which also gave rise to the Chromista
(the chromalveolate hypothesis).
However, as plastids only appear in
relatively advanced groups, others
argue the alveolates originally lacked
them and possibly the dinoflagellates
and Apicomplexa acquired them
separately.
[1] Fig. 1. A consensus phylogeny of
eukaryotes. The vast majority of
characterized eukaryotes, with the
notable exception of major subgroups of
amoebae, can now be assigned to one of
eight major groups. Opisthokonts (basal
flagellum) have a single basal
flagellum on reproductive cells and
flat mitochondrial cristae (most
eukaryotes have tubular ones).
Eukaryotic photosynthesis originated in
Plants; theirs are the only plastids
with just two outer membranes.
Heterokonts (different flagellae) have
a unique flagellum decorated with
hollow tripartite hairs (stramenopiles)
and, usually, a second plain one.
Cercozoans are amoebae with filose
pseudopodia, often living with in tests
(hard outer shells), some very
elaborate (foraminiferans). Amoebozoa
are mostly naked amoebae (lacking
tests), often with lobose pseudopodia
for at least part of their life cycle.
Alveolates have systems of cortical
alveoli directly beneath their plasma
membranes. Discicristates have discoid
mitochondrial cristae and, in some
cases, a deep (excavated) ventral
feeding groove. Amitochondrial
excavates lack substantial molecular
phylogenetic support, but most have an
excavated ventral feeding groove, and
all lack mitochondria. The tree shown
is based on a consensus of molecular
(1-4) and ultrastructural (16, 17) data
and includes a rough indication of new
ciPCR ''taxa'' (broken black lines)
(7-11). An asterisk preceding the taxon
name indicates probable paraphyletic
group COPYRIGHTED
source: http://www.sciencemag.org/cgi/co
ntent/full/300/5626/1703
[2] Figure 1. Phylogenetic hypothesis
of the eukaryotic lineage based on
ultrastructural and molecular data.
Organisms are divided into three main
groups distinguished by mitochondrial
cristal shape (either discoidal,
flattened or tubular). Unbroken lines
indicate phylogenetic relationships
that are firmly supported by available
data; broken lines indicate
uncertainties in phylogenetic
placement, resolution of which will
require additional data. Color coding
of organismal genus names indicates
mitochondrial genomes that have been
completely (Table 1), almost completely
(Jakoba, Naegleria and
Thraustochytrium) or partially (*)
sequenced by the OGMP (red), the FMGP
(black) or other groups (green). Names
in blue indicate those species whose
mtDNAs are currently being sequenced by
the OGMP or are future candidates for
complete sequencing. Amitochondriate
retortamonads are positioned at the
base of the tree, with broken arrows
denoting the endosymbiotic origin(s) of
mitochondria from a Rickettsia-like
eubacterium. Macrophar.,
Macropharyngomonas. COPYRIGHTED
source: http://nar.oxfordjournals.org/cg
i/content/full/26/4/865
Genetic comparison shows
the ancestor of the Chromalveolate
Alveolata Ciliates evolving now.
The ciliates are one of the most
important groups of protists, common
almost everywhere there is water -
lakes, ponds, oceans, and soils, with
many ecto- (lives on host) and
endosymbiotic (lives in host) members,
as well as some obligate (depends on
host for survival) and opportunistic
parasites (does not depend on host for
survival). Ciliates tend to be large
protists, a few reaching 2 mm in
length, and are some of the most
complex in structure. The name ciliate
comes from the presence of hair-like
organelles called cilia, which are
identical in structure to flagella but
typically shorter and present in much
larger numbers. Cilia occur in all
members of the group, although the
peculiar suctoria only have them for
part of the life-cycle, and are
variously used in swimming, crawling,
attachment, feeding, and sensation.
Unlike other eukaryotes, ciliates have
two different sorts of nuclei: a small,
diploid micronucleus (reproduction),
and a large, polyploid macronucleus
(general cell regulation). The latter
is generated from the micronucleus by
amplification of the genome and heavy
editing. The high degree of polyploidi
allows the cell to sustain an
appropriate level of transcription.
Division of the macronucleus does not
occur by a mitotic process but
segregation of the chromosomes is by a
different process, whose mechanism is
unknown. This process is not perfect,
and after about 200 generations the
cell shows signs of aging (has so many
mutations that it does not function
properly). Periodically the macronuclei
is (must be?) regenerated from the
micronuclei. In most, this occurs
during sexual reproduction, which is
not usually through syngamy but through
conjugation. Here two cells line up,
the micronuclei undergo meiosis, some
of the haploid daughters are exchanged
and then fuse to form new micro- and
macronuclei.
With a few exceptions, there is a
distinct cytostome or mouth where
ingestion takes place. Food vacuoles
are formed through phagocytosis and
typically follow a particular path
through the cell as their contents are
digested and broken down via lysosomes
so the substances the vacuole contains
are then small enough to diffuse
through the membrane of the food
vacuole into the cell. Anything left in
the food vacuole by the time it reaches
the cytoproct (anus) is discharged via
exocytosis. Most ciliates also have one
or more prominent contractile vacuoles,
which collect water and expel it from
the cell to maintain osmotic pressure,
or in some function to maintain ionic
balance. These often have a distinctive
star-shape, with each point being a
collecting tube.
Most ciliates feed on smaller organisms
(heterotrophic), such as bacteria and
algae, and detritus swept into the
mouth by modified oral cilia. These
usually include a series of
membranelles to the left of the mouth
and a paroral membrane to its right,
both of which arise from polykinetids,
groups of many cilia together with
associated structures. This varies
considerably, however. Some ciliates
are mouthless and feed by absorption,
while others are predatory and feed on
other protozoa and in particular on
other ciliates. This includes the
suctoria, which feed through several
specialized tentacles.
Ciliates and Amoeboids have in common:
Food is
digested in food vacuoles.
Excess water is
expelled by contractile vacuoles.
DOMAI
N Eukaryota - eukaryotes
KINGDOM Protozoa
(Goldfuss, 1818) R. Owen, 1858 -
protozoa
SUBKINGDOM Biciliata
INFRAKINGDOM
Alveolata Cavalier-Smith, 1991
PHYLUM Ciliophora (Doflein, 1901)
Copeland, 1956 - ciliates
CLASS
Karyorelictea
CLASS Heterotrichea
CLASS
Spirotrichea
CLASS Litostomatea
CLASS
Phyllopharyngea
CLASS Nassophorea
CLASS
Colpodea {possibly in phylum
percolozoa}
CLASS Prostomatea
CLASS
Oligohymenophorea
CLASS Plagiopylea
In some forms there are also body
polykinetids, for instance, among the
spirotrichs where they generally form
bristles called cirri. More often body
cilia are arranged in mono- and
dikinetids, which respectively include
one and two kinetosomes (basal bodies),
each of which may support a cilium.
These are arranged into rows called
kineties, which run from the anterior
to posterior of the cell. The body and
oral kinetids make up the
infraciliature, an organization unique
to the ciliates and important in their
classification, and include various
fibrils and microtubules involved in
coordinating the cilia.
The infraciliature is one of the main
component of the cell cortex. Another
are the alveoli, small vesicles under
the cell membrane that are packed
against it to form a pellicle
maintaining the cell's shape, which
varies from flexible and contractile to
rigid. Numerous mitochondria and
extrusomes are also generally present.
The presence of alveoli, the structure
of the cilia, the form of mitosis and
various other details indicate a close
relationship between the ciliates,
Apicomplexa, and dinoflagellates. These
superficially dissimilar groups make up
the alveolates.
Ciliates move by coordinated strokes of
hundreds of cilia projecting through
holes in a semirigid pellicle.
They discharge
long, barbed trichocysts for defense
and for capturing prey; toxicysts
release a poison.
Most are holozoic and ingest
food through a gullet and eliminate
wastes through an anal pore.
During asexual
reproduction, ciliates divide by
transverse binary fission.
Ciliates possess two
types of nuclei-a large macronucleus
and one or more small micronuclei.
a. The
macronucleus controls the normal
metabolism of the cell.
b. The
micronucleus are involved in sexual
reproduction.
1) The macronucleus disintegrates
and the micronucleus undergoes
meiosis.
2) Two ciliates then exchange a
haploid micronucleus.
3) The micronuclei give
rise to a new macronucleus containing
only housekeeping genes.
Ciliates are
diverse.
a. Members of the genus Paramecium
are complex. (Fig. 30.13b)
b. The
barrel-shaped didinia expand to consume
paramecia much larger than themselves.
c.
Suctoria rest on a stalk and paralyze
victims, sucking them dry.
d. Stentor
resembles a giant blue vase with
stripes. (Fig. 30.13a)
Could the 2 nuclei in ciliates be the
result of an earlier fusion (or
engulfing) of 2 prokaryotes?
[1] Fig. 1. A consensus phylogeny of
eukaryotes. The vast majority of
characterized eukaryotes, with the
notable exception of major subgroups of
amoebae, can now be assigned to one of
eight major groups. Opisthokonts (basal
flagellum) have a single basal
flagellum on reproductive cells and
flat mitochondrial cristae (most
eukaryotes have tubular ones).
Eukaryotic photosynthesis originated in
Plants; theirs are the only plastids
with just two outer membranes.
Heterokonts (different flagellae) have
a unique flagellum decorated with
hollow tripartite hairs (stramenopiles)
and, usually, a second plain one.
Cercozoans are amoebae with filose
pseudopodia, often living with in tests
(hard outer shells), some very
elaborate (foraminiferans). Amoebozoa
are mostly naked amoebae (lacking
tests), often with lobose pseudopodia
for at least part of their life cycle.
Alveolates have systems of cortical
alveoli directly beneath their plasma
membranes. Discicristates have discoid
mitochondrial cristae and, in some
cases, a deep (excavated) ventral
feeding groove. Amitochondrial
excavates lack substantial molecular
phylogenetic support, but most have an
excavated ventral feeding groove, and
all lack mitochondria. The tree shown
is based on a consensus of molecular
(1-4) and ultrastructural (16, 17) data
and includes a rough indication of new
ciPCR ''taxa'' (broken black lines)
(7-11). An asterisk preceding the taxon
name indicates probable paraphyletic
group COPYRIGHTED
source: http://www.sciencemag.org/cgi/co
ntent/full/300/5626/1703
[2] Figure 1. Phylogenetic hypothesis
of the eukaryotic lineage based on
ultrastructural and molecular data.
Organisms are divided into three main
groups distinguished by mitochondrial
cristal shape (either discoidal,
flattened or tubular). Unbroken lines
indicate phylogenetic relationships
that are firmly supported by available
data; broken lines indicate
uncertainties in phylogenetic
placement, resolution of which will
require additional data. Color coding
of organismal genus names indicates
mitochondrial genomes that have been
completely (Table 1), almost completely
(Jakoba, Naegleria and
Thraustochytrium) or partially (*)
sequenced by the OGMP (red), the FMGP
(black) or other groups (green). Names
in blue indicate those species whose
mtDNAs are currently being sequenced by
the OGMP or are future candidates for
complete sequencing. Amitochondriate
retortamonads are positioned at the
base of the tree, with broken arrows
denoting the endosymbiotic origin(s) of
mitochondria from a Rickettsia-like
eubacterium. Macrophar.,
Macropharyngomonas. COPYRIGHTED
source: http://nar.oxfordjournals.org/cg
i/content/full/26/4/865
Genetic Ribosomal
RNA comparison shows Chromalveolate
Alveolata, Dinoflagellates evolve.
Dinoflagellat
es reproduce mainly by haploid mitosis,
but also reproduce sexually.
In dinoflagellates, the chromosomes are
always visible and do not condense
prior to mitosis. The chromosomes are
attached to the nuclear envelope, which
persists during mitosis.
The main method of reproduction of the
dinoflagellates is by longitudinal cell
division, with each daughter cell
receiving one of the flagella ad a
portion of the theca and then
constructing the missing parts in a
very intricate sequence. Some
nonmotile species form zoospores, which
may be colonial. A number of species
reproduce sexually, mostly by isogamy,
but a few species reproduce by
heterogamy (anisogamy).
Dinoflagellate zygotes are similar to
some acritarchs (early eukaryote
fossils).
Some Dinoflagellates produce cysts.
The dinoflagellates are a large group
of flagellate protists. Most are marine
plankton, but they are common in fresh
water habitats as well; their
populations are distributed depending
on temperate, saltiness, or depth.
About half of all dinoflagellates are
photosynthetic, and these make up the
largest group of eukaryotic algae aside
from the diatoms. Being primary
producers make them an important part
of the food chain. Some species, called
zooxanthellae, are endosymbionts of
marine animals and protozoa, and play
an important part in the biology of
coral reefs. Other dinoflagellates are
colorless predators on other protozoa,
and a few forms are parasitic.
Some dinoflagellates are reported to be
filamentous (multicellular).
Mitochondri
a christae are tubular.
Dinoflagellates
are haploid (haplontic).
DOMAIN
Eukaryota - eukaryotes
KINGDOM Protozoa
(Goldfuss, 1818) R. Owen, 1858 -
protozoa
SUBKINGDOM Biciliata
INFRAKINGDOM
Alveolata Cavalier-Smith, 1991
PHYLUM Dinoflagellata Bütschli, 1885
CLASS Dinophyceae (Bütschli,
1885) Pascher, 1914
CLASS
Blastodiniophyceae Fensome et al.,
1993
CLASS Noctiluciphyceae
Fensome et al., 1993
CLASS
Syndiniophyceae Loeblich III, 1976
Most dinoflagellates are unicellular
forms with two dissimilar flagella. One
of these extends towards the posterior,
called the longitudinal flagellum,
while the other forms a lateral circle,
called the transverse flagellum. In
many forms these are set into grooves,
called the sulcus and cingulum. The
transverse flagellum provides most of
the force propelling the cell, and
often imparts to it a distinctive
whirling motion, which is what gives
the name dinoflagellate refers to
(Greek dinos, whirling). The
longitudinal acts mainly as the
steering wheel, but providing little
propulsive force as well.
Dinoflagellates have a complex cell
covering called an amphiesma, composed
of flattened vesicles, called alveoli.
In some forms, these support
overlapping cellulose plates that make
up a sort of armor called the theca.
These come in various shapes and
arrangements, depending on the species
and sometimes stage of the
dinoflagellate. Fibrous extrusomes are
also found in many forms. Together with
various other structural and genetic
details, this organization indicates a
close relationship between the
dinoflagellates, Apicomplexa, and
ciliates, collectively referred to as
the alveolates.
The chloroplasts in most photosynthetic
dinoflagellates are bound by three
membranes, suggesting they were
probably derived from some ingested
alga, and contain chlorophylls a and c
and fucoxanthin, as well as various
other accessory pigments. However, a
few have chloroplasts with different
pigmentation and structure, some of
which retain a nucleus. This suggests
that chloroplasts were incorporated by
several endosymbiotic events involving
already colored or secondarily
colorless forms. The discovery of
plastids in Apicomplexa have led some
to suggest they were inherited from an
ancestor common to the two groups, but
none of the more basal lines have them.
All the same, the dinoflagellate still
consists of the more common organelles
such as rough and smooth endoplasmic
reticulum, Golgi apparatus,
mitochondria, lipid and starch grains,
and food vacuoles. Some have even been
found with light sensitive organelle
such as the eyespot or a larger nucleus
containing a prominent nucleolus.
Life-cycle
Dinoflagellates have a peculiar form of
nucleus, called a dinokaryon, in which
the chromosomes are attached to the
nuclear membrane. These lack histones
and remained condensed throughout
interphase rather than just during
mitosis, which is closed and involves a
unique external spindle. This sort of
nucleus was once considered to be an
intermediate between the nucleoid
region of prokaryotes and the true
nuclei of eukaryotes, and so were
termed mesokaryotic, but now are
considered advanced rather than
primitive traits.
In most dinoflagellates, the nucleus is
dinokaryotic throughout the entire life
cycle. They are usually haploid, and
reproduce primarily through fission,
but sexual reproduction also occurs.
This takes place by fusion of two
individuals to form a zygote, which may
remain mobile in typical dinoflagellate
fashion or may form a resting cyst,
which later undergoes meiosis to
produce new haploid cells.
However, when the conditions become
desperate, usually starvation or no
light, their normal routines change
dramatically. Two dinoflagellates will
fuse together forming a planozygote.
Next is a stage not much different from
hibernation called hypnozygote when the
organism takes in excess fat and oil.
At the same time its shape is getting
fatter and the shell gets harder.
Sometimes even spikes are formed. When
the weathers allows it, these
dinoflagellates break out of their
shell and are in a temporary stage,
planomeiocyte, when they quickly
reforms their individual thecas and
return to the dinoflagellates at the
beginning of the process.
Ecology and fossils
Dinoflagellates sometimes
bloom in concentrations of more than a
million cells per millilitre. Some
species produce neurotoxins, which in
such quantities kill fish and
accumulate in filter feeders such as
shellfish, which in turn may pass them
on to people who eat them. This
phenomenon is called a red tide, from
the color the bloom imparts to the
water. Some colorless dinoflagellates
may also form toxic blooms, such as
Pfiesteria. It should be noted that not
all dinoflagellate blooms are
dangerous. Bluish flickers visible in
ocean water at night often come from
blooms of bioluminescent
dinoflagellates, which emit short
flashes of light when disturbed.
Dinoflagellate cysts are found as
microfossils from the Triassic period,
and form a major part of the
organic-walled marine microflora from
the middle Jurassic, through the
Cretaceous and Cenozoic to the present
day. Arpylorus, from the Silurian of
North Africa was at one time considered
to be a dinoflagellate cyst, but this
palynomorph is now considered to be
part of the microfauna. It is possible
that some of the Paleozoic acritarchs
also represent dinoflagellates.
Chloroplast features:
Chloroplasts:
Brown
Mitochondria christae are
tubular.
Nuclear features:
Gamete type:
flagellated
Dinoflagellates are
haploid (haplontic).
has condensed
chromosomes.
Mitotic spindle:
external.
polar structures: none, and
centrioles
Flagellar features:
Number of flagella:
2
Heterokont, isokont, or anisokont:
anisokont
shaft features: paraxial
rod, hairs
flagellate stages: gamete,
trophic, zoospore
trophic:
(trophozoites) The activated, feeding
stage in the life cycle of protozoan
parasites.
A protozoan, especially of
the class Sporozoa, in the active stage
of its life cycle.
The feeding stage of
a protozoan (as distinct from
reproductive or encysted stages).
zoospo
re: A zoospore is a motile asexual
spore utilizing a flagellum for
locomotion. Also called a swarm spore,
these spores are used by some algae and
fungi to propagate themselves.
Golgi type: dictyosome
Food stores:
carbohydrate: alpha 1-4
glucan
fat=yes
extrusomes: tricocysts, nematocysts
eyespot type: cytoplasmic stigma, ?
Life Forms:
unicellular: flagellate,
amoeboid, coccoid
multicellular:
filementous
Cell covering: pellicle with plates.
[1] Fig. 1. A consensus phylogeny of
eukaryotes. The vast majority of
characterized eukaryotes, with the
notable exception of major subgroups of
amoebae, can now be assigned to one of
eight major groups. Opisthokonts (basal
flagellum) have a single basal
flagellum on reproductive cells and
flat mitochondrial cristae (most
eukaryotes have tubular ones).
Eukaryotic photosynthesis originated in
Plants; theirs are the only plastids
with just two outer membranes.
Heterokonts (different flagellae) have
a unique flagellum decorated with
hollow tripartite hairs (stramenopiles)
and, usually, a second plain one.
Cercozoans are amoebae with filose
pseudopodia, often living with in tests
(hard outer shells), some very
elaborate (foraminiferans). Amoebozoa
are mostly naked amoebae (lacking
tests), often with lobose pseudopodia
for at least part of their life cycle.
Alveolates have systems of cortical
alveoli directly beneath their plasma
membranes. Discicristates have discoid
mitochondrial cristae and, in some
cases, a deep (excavated) ventral
feeding groove. Amitochondrial
excavates lack substantial molecular
phylogenetic support, but most have an
excavated ventral feeding groove, and
all lack mitochondria. The tree shown
is based on a consensus of molecular
(1-4) and ultrastructural (16, 17) data
and includes a rough indication of new
ciPCR ''taxa'' (broken black lines)
(7-11). An asterisk preceding the taxon
name indicates probable paraphyletic
group COPYRIGHTED
source: http://www.sciencemag.org/cgi/co
ntent/full/300/5626/1703
[2] Figure 1. Phylogenetic hypothesis
of the eukaryotic lineage based on
ultrastructural and molecular data.
Organisms are divided into three main
groups distinguished by mitochondrial
cristal shape (either discoidal,
flattened or tubular). Unbroken lines
indicate phylogenetic relationships
that are firmly supported by available
data; broken lines indicate
uncertainties in phylogenetic
placement, resolution of which will
require additional data. Color coding
of organismal genus names indicates
mitochondrial genomes that have been
completely (Table 1), almost completely
(Jakoba, Naegleria and
Thraustochytrium) or partially (*)
sequenced by the OGMP (red), the FMGP
(black) or other groups (green). Names
in blue indicate those species whose
mtDNAs are currently being sequenced by
the OGMP or are future candidates for
complete sequencing. Amitochondriate
retortamonads are positioned at the
base of the tree, with broken arrows
denoting the endosymbiotic origin(s) of
mitochondria from a Rickettsia-like
eubacterium. Macrophar.,
Macropharyngomonas. COPYRIGHTED
source: http://nar.oxfordjournals.org/cg
i/content/full/26/4/865
Genetic comparison
shows Apicomplexans evolve.
The
Apicomplexa are a large group of
protozoa, characterized by the presence
of an apical complex at some point in
their life-cycle. They are exclusively
parasitic, and completely lack flagella
or pseudopods except for certain gamete
stages. Diseases caused by Apicomplexa
include:
* Babesiosis (Babesia)
*
Cryptosporidiosis (Cryptosporidium)
* Malaria
(Plasmodium)
* Toxoplasmosis (Toxoplasma
gondii)
Most members have a complex life-cycle,
involving both asexual and sexual
reproduction. Typically, a host is
infected by ingesting cysts, which
divide to produce sporozoites that
enter its cells. Eventually, the cells
burst, releasing merozoites which
infect new cells. This may occur
several times, until gamonts are
produced, forming gametes that fuse to
create new cysts. There are many
variations on this basic pattern,
however, and many Apicomplexa have more
than one host.
DOMAIN Eukaryota -
eukaryotes
KINGDOM Protozoa (Goldfuss, 1818) R.
Owen, 1858 - protozoa
SUBKINGDOM Biciliata
INFRAKINGDOM Alveolata Cavalier-Smith,
1991
PHYLUM Apicomplexa
CLASS
Conoidasida Levine, 1988
CLASS
Aconoidasida Mehlhorn, Peters &
Haberkorn, 1980
CLASS
Metchnikovellea Weiser, 1977
CLASS
Blastocystea Cavalier-Smith, 1998
[1] Fig. 1. A consensus phylogeny of
eukaryotes. The vast majority of
characterized eukaryotes, with the
notable exception of major subgroups of
amoebae, can now be assigned to one of
eight major groups. Opisthokonts (basal
flagellum) have a single basal
flagellum on reproductive cells and
flat mitochondrial cristae (most
eukaryotes have tubular ones).
Eukaryotic photosynthesis originated in
Plants; theirs are the only plastids
with just two outer membranes.
Heterokonts (different flagellae) have
a unique flagellum decorated with
hollow tripartite hairs (stramenopiles)
and, usually, a second plain one.
Cercozoans are amoebae with filose
pseudopodia, often living with in tests
(hard outer shells), some very
elaborate (foraminiferans). Amoebozoa
are mostly naked amoebae (lacking
tests), often with lobose pseudopodia
for at least part of their life cycle.
Alveolates have systems of cortical
alveoli directly beneath their plasma
membranes. Discicristates have discoid
mitochondrial cristae and, in some
cases, a deep (excavated) ventral
feeding groove. Amitochondrial
excavates lack substantial molecular
phylogenetic support, but most have an
excavated ventral feeding groove, and
all lack mitochondria. The tree shown
is based on a consensus of molecular
(1-4) and ultrastructural (16, 17) data
and includes a rough indication of new
ciPCR ''taxa'' (broken black lines)
(7-11). An asterisk preceding the taxon
name indicates probable paraphyletic
group COPYRIGHTED
source: http://www.sciencemag.org/cgi/co
ntent/full/300/5626/1703
[2] Figure 1. Phylogenetic hypothesis
of the eukaryotic lineage based on
ultrastructural and molecular data.
Organisms are divided into three main
groups distinguished by mitochondrial
cristal shape (either discoidal,
flattened or tubular). Unbroken lines
indicate phylogenetic relationships
that are firmly supported by available
data; broken lines indicate
uncertainties in phylogenetic
placement, resolution of which will
require additional data. Color coding
of organismal genus names indicates
mitochondrial genomes that have been
completely (Table 1), almost completely
(Jakoba, Naegleria and
Thraustochytrium) or partially (*)
sequenced by the OGMP (red), the FMGP
(black) or other groups (green). Names
in blue indicate those species whose
mtDNAs are currently being sequenced by
the OGMP or are future candidates for
complete sequencing. Amitochondriate
retortamonads are positioned at the
base of the tree, with broken arrows
denoting the endosymbiotic origin(s) of
mitochondria from a Rickettsia-like
eubacterium. Macrophar.,
Macropharyngomonas. COPYRIGHTED
source: http://nar.oxfordjournals.org/cg
i/content/full/26/4/865
(the Phyla "Radiolaria", "Cercozoa",
and "Foraminifera") evolve now.
This marks the beginning of the
protists described as "amoeboid",
because they have pseudopods.
5. Amoeboids
phagocytize their food; pseudopods
surround and engulf prey.
6. Food is digested
inside food vacuoles.
7. Freshwater amoeboids
have contractile vacuoles to eliminate
excess water.
Some foraminifera are haplodiploid
(alternate between haploid and diploid
cycles that both have mitosis).
The Rhizaria are a major line of
protists. They vary considerably in
form, but for the most part they are
amoeboids with filose, reticulose, or
microtubule-supported pseudopods. Many
produce shells or skeletons, which may
be quite complex in structure, and
these make up the vast majority of
protozoan fossils. Nearly all have
mitochondria with tubular cristae.
There
are three main groups of Rhizaria:
Cercozoa
Various amoebae and flagellates,
usually with filose pseudopods and
common in soil
Foraminifera Amoeboids with
reticulose pseudopods, common as marine
benthos
Radiolaria Amoeboids with axopods,
common as marine plankton
The name Rhizaria was created recently
by Cavalier-Smith in 2002. Most are
biciliate amoeboflagellates at some
point in the life cycle. Pseudopodia
are root-like reticulopodia, filopodia
and/or axopodia - not broad lobopodia
as in Amoeba. All of these features
can, however, be found in members of
other clades. Nevertheless, the
Rhizaria are supported by both rRNA and
actin trees (Cavalier-Smith & Chao,
2003; Nikolaev et al. 2004).
A few
other groups may be included in the
Cercozoa, but on some trees appear
closer to the Foraminifera. These are
the Phytomyxea and Ascetosporea,
parasites of plants and animals
respectively, and the peculiar amoeba
Gromia. The different groups of
Rhizaria are considered close relatives
based mainly on genetic similarities,
and have been regarded as an extension
of the Cercozoa. The name Rhizaria for
the expanded group was introduced by
Cavalier-Smith in 2002, who also
included the centrohelids and Apusozoa.
[1] FIG. 2. The tree of life based on
molecular, ultrastructural and
palaeontological evidence. Contrary to
widespread assumptions, the root is
among the eubacteria, probably within
the double-enveloped Negibacteria, not
between eubacteria and archaebacteria
(Cavalier-Smith, 2002b); it may lie
between Eobacteria and other
Negibacteria (Cavalier-Smith, 2002b).
The position of the eukaryotic root has
been nearly as controversial, but is
less hard to establish: it probably
lies between unikonts and bikonts (Lang
et al., 2002; Stechmann and
Cavalier-Smith, 2002, 2003). For
clarity the basal eukaryotic kingdom
Protozoa is not labelled; it comprises
four major groups (alveolates, cabozoa,
Amoebozoa and Choanozoa) plus the small
bikont phylum Apusozoa of unclear
precise position; whether Heliozoa are
protozoa as shown or chromists is
uncertain (Cavalier-Smith, 2003b).
Symbiogenetic cell enslavement occurred
four or five times: in the origin of
mitochondria and chloroplasts from
different negibacteria, of
chromalveolates by the enslaving of a
red alga (Cavalier-Smith, 1999, 2003;
Harper and Keeling, 2003) and in the
origin of the green plastids of
euglenoid (excavate) and chlorarachnean
(cercozoan) algae-a green algal cell
was enslaved either by the ancestral
cabozoan (arrow) or (less likely) twice
independently within excavates and
Cercozoa (asterisks) (Cavalier-Smith,
2003a). The upper thumbnail sketch
shows membrane topology in the
chimaeric cryptophytes (class
Cryptophyceae of the phylum Cryptista);
in the ancestral chromist the former
food vacuole membrane fused with the
rough endoplasmic reticulum placing the
enslaved cell within its lumen (red) to
yield the complex membrane topology
shown. The large host nucleus and the
tiny nucleomorph are shown in blue,
chloroplast green and mitochondrion
purple. In chlorarachneans (class
Chlorarachnea of phylum Cercozoa) the
former food vacuole membrane remained
topologically distinct from the ER to
become an epiplastid membrane and so
did not acquire ribosomes on its
surface, but their membrane topology is
otherwise similar to the cryptophytes.
The other sketches portray the four
major kinds of cell in the living world
and their membrane topology. The upper
ones show the contrasting ancestral
microtubular cytoskeleton (ciliary
roots, in red) of unikonts (a cone of
single microtubules attaching the
single centriole to the nucleus, blue)
and bikonts (two bands of microtubules
attached to the posterior centriole and
an anterior fan of microtubules
attached to the anterior centriole).
The lower ones show the single plasma
membrane of unibacteria (posibacteria
plus archaebacteria), which were
ancestral to eukaryotes and the double
envelope of negibacteria, which were
ancestral to mitochondria and
chloroplasts (which retained the outer
membrane, red).
source: http://aob.oxfordjournals.org/cg
i/content/full/95/1/147/FIG2
[2] Fig. 1. A consensus phylogeny of
eukaryotes. The vast majority of
characterized eukaryotes, with the
notable exception of major subgroups of
amoebae, can now be assigned to one of
eight major groups. Opisthokonts (basal
flagellum) have a single basal
flagellum on reproductive cells and
flat mitochondrial cristae (most
eukaryotes have tubular ones).
Eukaryotic photosynthesis originated in
Plants; theirs are the only plastids
with just two outer membranes.
Heterokonts (different flagellae) have
a unique flagellum decorated with
hollow tripartite hairs (stramenopiles)
and, usually, a second plain one.
Cercozoans are amoebae with filose
pseudopodia, often living with in tests
(hard outer shells), some very
elaborate (foraminiferans). Amoebozoa
are mostly naked amoebae (lacking
tests), often with lobose pseudopodia
for at least part of their life cycle.
Alveolates have systems of cortical
alveoli directly beneath their plasma
membranes. Discicristates have discoid
mitochondrial cristae and, in some
cases, a deep (excavated) ventral
feeding groove. Amitochondrial
excavates lack substantial molecular
phylogenetic support, but most have an
excavated ventral feeding groove, and
all lack mitochondria. The tree shown
is based on a consensus of molecular
(1-4) and ultrastructural (16, 17) data
and includes a rough indication of new
ciPCR ''taxa'' (broken black lines)
(7-11). An asterisk preceding the taxon
name indicates probable paraphyletic
group.
source: http://www.sciencemag.org/cgi/co
ntent/full/300/5626/1703
now.
The Cercozoa are a group of protists,
including most amoeboids and
flagellates that feed by means of
filose pseudopods. These may be
restricted to part of the cell surface,
but there is never a true cytostome or
mouth as found in many other protozoa.
They show a variety of forms and have
proven difficult to define in terms of
structural characteristics, although
their unity is strongly supported by
genetic studies.
The best-known Cercozoa are
the euglyphids, filose amoebae with
shells of siliceous scales or plates,
which are commonly found in soils,
nutrient-rich waters, and on aquatic
plants. Some other filose amoebae
produce organic shells, including the
tectofilosids and Gromia. They were
formerly classified with the euglyphids
as the Testaceafilosia. This group is
not monophyletic, but nearly all
studied members fall in or near the
Cercozoa, related to similarly shelled
flagellates.
Another important group placed here are
the chlorarachniophytes, strange
amoebae that form a reticulating net.
They are set apart by the presence of
chloroplasts, which apparently
developed from an ingested green alga.
They are bound by four membranes and
still possess a vestigial nucleus,
called a nucleomorph. As such, they
have been of great interest to
researchers studying the endosymbiotic
origins of organelles.
Other notable cercozoans include the
cercomonads, which are common soil
flagellates. Two groups traditionally
considered heliozoa, the dimorphids and
desmothoracids, belong here. Recently
the marine Phaeodarea have also been
included. The Cercozoa are closely
related to the Foraminifera and
Radiolaria, amoeboids that usually have
complex shells, and together with them
form a supergroup called the Rhizaria.
Their exact composition and
relationships are still being worked
out.
PHYLUM Cercozoa (Cavalier-Smith 1998)
CLASS Spongomonadea
CLASS Proteomyxidea -
desmothoracids, dimorphids,
gymnophryids, etc.
CLASS Sarcomonadea -
cercomonads
CLASS Imbricatea - euglyphids and
thaumatomonads
CLASS Thecofilosea - tectofilosids
and cryomonads
CLASS Phaeodarea
CLASS Chlorarachnea
(Hibberd & Norris, 1984)
Class Spongomonadea
Chlorarachniophytes
are a small group of algae occasionally
found in tropical oceans. They are
typically mixotrophic, ingesting
bacteria and smaller protists as well
as conducting photosynthesis. Normally
they have the form of small amoebae,
with branching cytoplasmic extensions
that capture prey and connect the cells
together, forming a net. They may also
form flagellate zoospores, which
characteristically have a single
subapical flagellum that spirals
backwards around the cell body, and
walled coccoid cells.
The chloroplasts were presumably
acquired by ingesting some green alga.
They are surrounded by four membranes,
the outermost of which is continuous
with the endoplasmic reticulum, and
contain a small nucleomorph between the
middle two, which is a remnant of the
alga's nucleus. This contains a small
amount of DNA and divides without
forming a mitotic spindle. The origin
of the chloroplasts from green algae is
supported by their pigmentation, which
includes chlorophylls a and b, and by
genetic similarities. The only other
group of algae that contain
nucleomorphs are the cryptomonads, but
their chloroplasts seem to be derived
from a red alga.
The chlorarachniophytes only include
five genera, which show some variation
in their life-cycles and may lack one
or two of the stages described above.
Genetic studies place them among the
Cercozoa, a diverse group of amoeboid
and amoeboid-like protozoa.
Class Proteomyxidea
Order Desmothoracida (Hertwig &
Lesser 1874)
The desmothoracids are a group
of heliozoan protists, usually sessile
and found in freshwater environments.
Each adult is a spherical cell around
10-20 μm in diameter surrounded by
a perforated organic lorica or shell,
with many radial pseudopods projecting
through the holes to capture food.
These are supported by small bundles of
microtubules that arise near a point on
the nuclear membrane. Unlike other
heliozoans, the microtubules are not in
any regular geometric array, there does
not appear to be a microtubule
organizing center, and there is no
distinction between the outer and inner
cytoplasm.
Reproduction takes place by the budding
off of small motile cells, usually with
two flagella. Later these are lost, and
pseudopods and a lorica are formed.
Typically a single lengthened pseudopod
will secrete a hollow stalk that
attached the adult to the substrate.
The form of the flagella, the tubular
cristae within the mitochondria, and
other characters led to the suggestion
that the desmothoracids belong among
what is now the Cercozoa, which has now
been confirmed by genetic studies.
Order Heliomonadida
Genus Dimorpha
The dimorphids or
heliomonads are a small group of
heliozoa that are unusual in possessing
flagella throughout their life-cycle.
There are two genera: Dimorpha, a tiny
organism found in freshwater, and the
larger Tetradimorpha, which is
distinguished by having four rather
than two flagella. Bundles of
microtubules, typically in square
array, arise from a body near the
flagellar bases and support the
numerous axopods that project from the
cell surface.
Dimorphids have a single nucleus, and
mitochondria with tubular cristae.
Genetic studies place them among the
Cercozoa, a group including various
other flagellates that form pseudopods.
Order Reticulosida
Family Gymnophryidae (Mikrjukov &
Mylnikov, 1996)
The gymnophryids are a small
group of amoeboids that lack shells and
produce thin, reticulose pseudopods.
These contain microtubules and have a
granular appearance, owing to the
presence of extrusomes, but are
distinct from the pseudopods of
Foraminifera. They are included among
the Cercozoa, but differ from other
cercozoans in having mitochondria with
flat cristae, rather than tubular
cristae.
Gymnophrys cometa, found in freshwater
and soil, is representative of the
group. The cell body is under 10
μm in size, and has a pair of
reduced flagella, which are smooth and
insert parallel to one another. It may
also produce motile zoospores and
cysts. Gymnophrys and Borkovia are the
only confirmed genera, but other naked
reticulose amoebae such as Biomyxa may
be close relatives.
Class Sarcomonadea
Order Cercomonadida (Poche,
1913)
Cercomonads are small flagellates,
widespread in aqueous habitats and
especially common in soils. The cells
are generally around 10 μm in
length, without any shell or covering.
They produce filose pseudopods to
capture bacteria, but do not use them
for locomotion, which usually takes
place by gliding along surfaces. Most
members have two smooth flagella, one
directed forward and one trailing under
the cell, inserted at right angles near
its anterior. The nucleus is connected
to the flagellar bases and accompanied
by a characteristic paranuclear body.
Genetic studies place the cercomonads
among the core Cercozoa, a diverse
group of amoeboid and flagellate
protozoans. They are divided into two
families. The Heteromitidae tend to be
relatively rigid, and produce only
temporary pseudopods. The
Cercomonadidae are more plastic, and
when food supplies are plentiful may
become amoeboid and even multinucleate.
The classification of genera and
species continues to undergo revision.
Some genera have been merged, like
Cercomonas and Cercobodo, and some have
been moved to other groups.
Class Imbricatea
Order Euglyphida (Copeland,
1956)
The euglyphids are a prominent group of
filose amoebae that produce shells or
tests from siliceous scales, plates,
and sometimes spines. These elements
are created within the cell and then
assembled on its surface in a more or
less regular arrangement, giving the
test a textured appearance. There is a
single opening for the long slender
pseudopods, which capture food and pull
the cell across the substrate.
Euglyphids are common in soils,
marshes, and other organic-rich
environments, feeding on tiny organisms
such as bacteria. The test is generally
30-100 μm in length, although the
cell only occupies part of this space.
During reproduction a second shell is
formed opposite the opening, so both
daughter cells remain protected.
Different genera and species are
distinguished primarily by the form of
the test. Euglypha and Trinema are the
most common.
The euglyphids are traditionally
grouped with other amoebae. However,
genetic studies instead place them with
various amoeboid and flagellate groups,
forming an assemblage called the
Cercozoa. Their closest relatives are
the thaumatomonads, flagellates that
form similar siliceous tests.
Class Thecofilosea
Order Tectofilosida
(Cavalier-Smith & Chao, 2003)
The
tectofilosids or amphitremids are a
group of filose amoebae with shells.
These are composed of organic materials
and sometimes collected debris, in
contrast to the euglyphids, which
produce shells from siliceous scales.
The shell usually has a single opening,
but in Amphitrema and a few other
genera it has two on opposite ends. The
cell itself occupies most of the shell.
They are most often found on marsh
plants such as Sphagnum.
This group was previously classified as
the Gromiida or Gromiina. However,
molecular studies separate Gromia from
the others, which must therefore be
renamed. They are placed among the
Cercozoa, and presumably developed from
flagellates like Cryothecomonas, which
has a similar test. However, only a few
have been studied in detail, so their
relationships and monophyly are not yet
certain.
Class: Phaeodarea (Haeckel, 1879)
The
Phaeodarea are a group of amoeboid
protists. They are traditionally
considered radiolarians, but in
molecular trees do not appear to be
close relatives of the other groups,
and are instead placed among the
Cercozoa. They are distinguished by the
structure of their central capsule and
by the presence of a phaeodium, an
aggregate of waste particles within the
cell.
Phaeodarea produce hollow skeletons
composed of amorphous silica and
organic material, which rarely
fossilize. The endoplasm is divided by
a cape with three openings, of which
one gives rise to feeding pseudopods,
and the others let through bundles of
microtubules that support the axopods.
Unlike other radiolarians, there are no
cross-bridges between them. They also
lack symbiotic algae, generally living
below the photic zone, and do not
produce any strontium sulphate.
CLASS Chlorarachnea
Chlorarachniophytes are a small
group of algae occasionally found in
tropical oceans. They are typically
mixotrophic, ingesting bacteria and
smaller protists as well as conducting
photosynthesis. Normally they have the
form of small amoebae, with branching
cytoplasmic extensions that capture
prey and connect the cells together,
forming a net. They may also form
flagellate zoospores, which
characteristically have a single
subapical flagellum that spirals
backwards around the cell body, and
walled coccoid cells.
The chloroplasts were presumably
acquired by ingesting some green alga.
They are surrounded by four membranes,
the outermost of which is continuous
with the endoplasmic reticulum, and
contain a small nucleomorph between the
middle two, which is a remnant of the
alga's nucleus. This contains a small
amount of DNA and divides without
forming a mitotic spindle. The origin
of the chloroplasts from green algae is
supported by their pigmentation, which
includes chlorophylls a and b, and by
genetic similarities. The only other
group of algae that contain
nucleomorphs are the cryptomonads, but
their chloroplasts seem to be derived
from a red alga.
The chlorarachniophytes only include
five genera, which show some variation
in their life-cycles and may lack one
or two of the stages described above.
Genetic studies place them among the
Cercozoa, a diverse group of amoeboid
and amoeboid-like protozoa.
[1] FIG. 2. The tree of life based on
molecular, ultrastructural and
palaeontological evidence. Contrary to
widespread assumptions, the root is
among the eubacteria, probably within
the double-enveloped Negibacteria, not
between eubacteria and archaebacteria
(Cavalier-Smith, 2002b); it may lie
between Eobacteria and other
Negibacteria (Cavalier-Smith, 2002b).
The position of the eukaryotic root has
been nearly as controversial, but is
less hard to establish: it probably
lies between unikonts and bikonts (Lang
et al., 2002; Stechmann and
Cavalier-Smith, 2002, 2003). For
clarity the basal eukaryotic kingdom
Protozoa is not labelled; it comprises
four major groups (alveolates, cabozoa,
Amoebozoa and Choanozoa) plus the small
bikont phylum Apusozoa of unclear
precise position; whether Heliozoa are
protozoa as shown or chromists is
uncertain (Cavalier-Smith, 2003b).
Symbiogenetic cell enslavement occurred
four or five times: in the origin of
mitochondria and chloroplasts from
different negibacteria, of
chromalveolates by the enslaving of a
red alga (Cavalier-Smith, 1999, 2003;
Harper and Keeling, 2003) and in the
origin of the green plastids of
euglenoid (excavate) and chlorarachnean
(cercozoan) algae-a green algal cell
was enslaved either by the ancestral
cabozoan (arrow) or (less likely) twice
independently within excavates and
Cercozoa (asterisks) (Cavalier-Smith,
2003a). The upper thumbnail sketch
shows membrane topology in the
chimaeric cryptophytes (class
Cryptophyceae of the phylum Cryptista);
in the ancestral chromist the former
food vacuole membrane fused with the
rough endoplasmic reticulum placing the
enslaved cell within its lumen (red) to
yield the complex membrane topology
shown. The large host nucleus and the
tiny nucleomorph are shown in blue,
chloroplast green and mitochondrion
purple. In chlorarachneans (class
Chlorarachnea of phylum Cercozoa) the
former food vacuole membrane remained
topologically distinct from the ER to
become an epiplastid membrane and so
did not acquire ribosomes on its
surface, but their membrane topology is
otherwise similar to the cryptophytes.
The other sketches portray the four
major kinds of cell in the living world
and their membrane topology. The upper
ones show the contrasting ancestral
microtubular cytoskeleton (ciliary
roots, in red) of unikonts (a cone of
single microtubules attaching the
single centriole to the nucleus, blue)
and bikonts (two bands of microtubules
attached to the posterior centriole and
an anterior fan of microtubules
attached to the anterior centriole).
The lower ones show the single plasma
membrane of unibacteria (posibacteria
plus archaebacteria), which were
ancestral to eukaryotes and the double
envelope of negibacteria, which were
ancestral to mitochondria and
chloroplasts (which retained the outer
membrane, red).
source: http://aob.oxfordjournals.org/cg
i/content/full/95/1/147/FIG2
[2] Fig. 1. A consensus phylogeny of
eukaryotes. The vast majority of
characterized eukaryotes, with the
notable exception of major subgroups of
amoebae, can now be assigned to one of
eight major groups. Opisthokonts (basal
flagellum) have a single basal
flagellum on reproductive cells and
flat mitochondrial cristae (most
eukaryotes have tubular ones).
Eukaryotic photosynthesis originated in
Plants; theirs are the only plastids
with just two outer membranes.
Heterokonts (different flagellae) have
a unique flagellum decorated with
hollow tripartite hairs (stramenopiles)
and, usually, a second plain one.
Cercozoans are amoebae with filose
pseudopodia, often living with in tests
(hard outer shells), some very
elaborate (foraminiferans). Amoebozoa
are mostly naked amoebae (lacking
tests), often with lobose pseudopodia
for at least part of their life cycle.
Alveolates have systems of cortical
alveoli directly beneath their plasma
membranes. Discicristates have discoid
mitochondrial cristae and, in some
cases, a deep (excavated) ventral
feeding groove. Amitochondrial
excavates lack substantial molecular
phylogenetic support, but most have an
excavated ventral feeding groove, and
all lack mitochondria. The tree shown
is based on a consensus of molecular
(1-4) and ultrastructural (16, 17) data
and includes a rough indication of new
ciPCR ''taxa'' (broken black lines)
(7-11). An asterisk preceding the taxon
name indicates probable paraphyletic
group.
source: http://www.sciencemag.org/cgi/co
ntent/full/300/5626/1703
evolve now.
Ribosomal RNA indicates that
Rhizaria Phylum "Radiolaria" evolve
now.
Radiolarians (also radiolaria) are
amoeboid protozoa that produce
intricate mineral skeletons, typically
with a central capsule dividing the
cell into inner and outer portions,
called endoplasm and ectoplasm. They
are found as plankton throughout the
ocean, and their shells are important
fossils found from the Cambrian
onwards.
Move by pseudopodia.
external tests
made of silica (glass).
Radiolaria have a test composed of
silica or strontium sulfate.
Most have a radial
arrangement of spines.
Pseudopods (actinopods)
project from an external layer of
cytoplasm and are supported by rows of
microtubules.
Tests of dead foraminiferans and
radiolarians form deep layers of ocean
floor sediment.
Back to the Precambrian, each
layer has distinctive foraminiferans
which helps date rocks.
Over hundreds of
millions of years, the CaCO3 shells
have contributed to the formation of
chalk deposits (i.e. White Cliffs of
Dover, limestone of pyramids).
Lifecycle
Simple asexual fission of radiolarian
cells has been observed. Sexual
reproduction has not been confirmed but
is assumed to occur; possible
gametogenesis has been observed in the
form of "swarmers" being expelled from
swellings in the cell. Swarmers are
formed from the central capsule after
the ectoplasm has been discarded. The
central capsule sinks through the water
column to depths hundreds of meters
greater than the normal habitat and
swells, eventually rupturing and
releasing the flagellated cells.
Recombination of these cells, which are
assumed to be haploid, to produce
diploid "adults" has not been observed
however and is only inferred to occur.
Comparisons of standing crops within
the water column and sediment trap
samples have ascertained that the
average life span of radiolarians is
about two weeks, ranging from a few
days to a few weeks.
All radiolarians
secrete strontium sulphate at some
point in the life cycle - as the adult
shell in Acantharea, and as crystals in
swarmer cells" produced during
asexual reproduction in Polycystinea.
La
rge, planktonic forms that produce a
glassy, intricate shell.
Radiolarians have many needle-like
pseudopods supported by microtubules,
called axopods, which aid in flotation.
The nuclei and most other organelles
are in the endoplasm, while the
ectoplasm is filled with frothy
vacuoles and lipid droplets, keeping
them buoyant. Often it also contains
symbiotic algae, especially
zooxanthellae, that provide most of the
cell's energy. Some of this
organization is found among the
heliozoa, but those lack central
capsules and only produce simple scales
and spines.
The main class of radiolarians are the
Polycystinea, which produce siliceous
skeletons. These include the majority
of fossils. They also include the
Acantharea, which produce skeletons of
strontium sulfate. Despite some initial
suggestions to the contrary, genetic
studies place these two groups close
together. They also include the
peculiar genus Sticholonche, which
lacks an internal skeleton and so is
usually considered a heliozoan.
Traditionally the radiolarians also
include the Phaeodarea, which produce
siliceous skeletons but differ from the
polycystines in several other respects.
However, on molecular trees they branch
with the Cercozoa, a group including
various flagellate and amoeboid
protists. The other radiolarians appear
near, but outside, the Cercozoa, so the
similarity is due to convergent
evolution. The radiolarians and
Cercozoa are included within a
supergroup called the Rhizaria.
German biologist Ernst Haeckel produced
exquisite (and perhaps somewhat
exaggerated) drawings of radiolaria,
helping to popularize these protists
among Victorian parlor microscopists
alongside foraminifera and diatoms.
PHYL
UM Radiolaria (Müller 1858 emend.)
CLASS Polycystinea
CLASS Acantharea
(Haeckel, 1881)
CLASS Sticholonchea
(CLASS Phaeodarea Haeckel, 1879 )?
CLASS Polycystinea:
The polycystines are a group of
radiolarian protists. They include the
vast majority of the fossil radiolaria,
as their skeletons are abundant in
marine sediments, making them one of
the most common groups of microfossils.
These skeletons are composed of opaline
silica. In some it takes the form of
relatively simple spicules, but in
others it forms more elaborate
lattices, such as concentric spheres
with radial spines or sequences of
conical chambers.
Class Acantharea
The Acantharea are a small group
of radiolarian protozoa, distinguished
mainly by their skeletons. These are
composed of strontium sulfate crystals,
which do not fossilize, and take the
form of either ten diametric or twenty
radial spines. The central capsule is
made up of microfibrils arranged into
twenty plates, each with a hole through
which one spine projects, and there is
also a microfibrillar cortex linked to
the spines by myonemes. These assist in
flotation, together with the vacuoles
in the ectoplasm, which often contain
zooxanthellae.
The axopods are fixed in
number. Reproduction takes place by
formation of spores, which may be
flagellate. These develop into
mononucleate amoebae; adults are
usually multinucleate.
Class Sticholonchea
Sticholonche is a peculiar genus
of protozoan with a single species, S.
zanclea, found in open oceans at depths
of 100-500 metres. It is generally
considered a heliozoan, placed in its
own order, called the Taxopodida.
However it has also been classified as
an unusual radiolarian, and this has
gained support from genetic studies,
which place it near the Acantharea.
Sticholonche are usually around 200
μm, though this varies
considerably, and have a bilaterally
symmetric shape, somewhat flattened and
widened at the front. The axopods are
arranged into distinct rows, six of
which lie in a dorsal groove and are
rigid, and the rest of which are
mobile. These are used primarily for
buoyancy, rather than feeding. They
also have fourteen groups of prominent
spines, and many smaller spicules,
although there is no central capsule as
in true radiolarians.
Cercozoa, originally named by
Cavalier-Smith in 1998, is a diverse
group of taxa united solely on
molecular grounds, but supported by a
number of genes (Longet et al., 2003).
Amongst notable members of the Cercozoa
are amoeboid forms such as Difflugia,
which produce agglutinated tests that
may be fossilised (the record extends
back to the Neoproterozoic - Finlay
et al., 2004), and the Chlorarachnea
(e.g. Chlorarachnion), marine amoeboid
organisms which possess chloroplasts
derived from a secondary endosymbiosis
with a green alga. Cavalier-Smith,
(2003). The nucleus of the endosymbiont
in Chlorarachnion, in fact, has not
fully degraded as in most secondarily
plastid-bearing eukaryotes, and the
chloroplast retains a small nucleomorph
contained within the surrounding
membranes.
The Polycystinea (sometimes spelled
Polycistinea or Polycystina) are one
group of the Radiolaria. These are not
just "small shelly fauna," they are
tiny shelly fauna made up of single, if
rather complex, cells. The shell turns
out to be made of amorphous silica --
essentially sand -- without the
admixture of organics that characterize
similar forms. Polycystinea are
exclusively marine but found in great
numbers in the oceans. Their fossil
record goes back almost a billion
years, well into Precambrian time.
Like other radiolarians, the cytoplasm
of Polycystinea is divided into
ectoplasm and endoplasm by a perforated
protein capsule -- not the nuclear
membrane, but a novel structure unique
to this group. The endoplasm forms a
central medulla enclosed by this
porous, membranous capsule. The nucleus
is inside this central region. The
ectoplasm is outside the capsule and
forms the region known as the cortex
(or calymma). The visible remains shown
in the image are made up of perforated
tests (the "shells"). In life, these
are located in the ectoplasm.
Polycystinates extend pseudopods
supported by a complex microtubular
array (axopods) which originate in the
endoplasm. The pseudopods pass through
pores in the test and extend, covered
with a thin layer of cytoplasm, from
the surface of the cell. Spines of the
test, if any, also pass through the
capsule and extend, covered with
cytoplasm, from the surface of the
cell. The ectoplasm is often vacuolated
and frequently contains photosynthetic
zooxanthellae.
The endoplasm actually contains all of
the organelles normally associated with
a "normal" heterotrophic eukaryotic
cell, including mitochondria, a
nucleus, and a cytoskeleton. The
ectoplasm is largely filled with
digestive vacuoles, symbiotic algae,
and the test. From an evolutionary
standpoint, the Polycystina appear to
be one step towards a whole different
type of biological organization based
on a 3-compartment cell, rather than
the 2-compartment cell of metazoans. In
fact, a number of polycystinean species
are colonial. It is interesting to
speculate on what might have evolved on
this model, had circumstances been
different.
[1] FIG. 2. The tree of life based on
molecular, ultrastructural and
palaeontological evidence. Contrary to
widespread assumptions, the root is
among the eubacteria, probably within
the double-enveloped Negibacteria, not
between eubacteria and archaebacteria
(Cavalier-Smith, 2002b); it may lie
between Eobacteria and other
Negibacteria (Cavalier-Smith, 2002b).
The position of the eukaryotic root has
been nearly as controversial, but is
less hard to establish: it probably
lies between unikonts and bikonts (Lang
et al., 2002; Stechmann and
Cavalier-Smith, 2002, 2003). For
clarity the basal eukaryotic kingdom
Protozoa is not labelled; it comprises
four major groups (alveolates, cabozoa,
Amoebozoa and Choanozoa) plus the small
bikont phylum Apusozoa of unclear
precise position; whether Heliozoa are
protozoa as shown or chromists is
uncertain (Cavalier-Smith, 2003b).
Symbiogenetic cell enslavement occurred
four or five times: in the origin of
mitochondria and chloroplasts from
different negibacteria, of
chromalveolates by the enslaving of a
red alga (Cavalier-Smith, 1999, 2003;
Harper and Keeling, 2003) and in the
origin of the green plastids of
euglenoid (excavate) and chlorarachnean
(cercozoan) algae-a green algal cell
was enslaved either by the ancestral
cabozoan (arrow) or (less likely) twice
independently within excavates and
Cercozoa (asterisks) (Cavalier-Smith,
2003a). The upper thumbnail sketch
shows membrane topology in the
chimaeric cryptophytes (class
Cryptophyceae of the phylum Cryptista);
in the ancestral chromist the former
food vacuole membrane fused with the
rough endoplasmic reticulum placing the
enslaved cell within its lumen (red) to
yield the complex membrane topology
shown. The large host nucleus and the
tiny nucleomorph are shown in blue,
chloroplast green and mitochondrion
purple. In chlorarachneans (class
Chlorarachnea of phylum Cercozoa) the
former food vacuole membrane remained
topologically distinct from the ER to
become an epiplastid membrane and so
did not acquire ribosomes on its
surface, but their membrane topology is
otherwise similar to the cryptophytes.
The other sketches portray the four
major kinds of cell in the living world
and their membrane topology. The upper
ones show the contrasting ancestral
microtubular cytoskeleton (ciliary
roots, in red) of unikonts (a cone of
single microtubules attaching the
single centriole to the nucleus, blue)
and bikonts (two bands of microtubules
attached to the posterior centriole and
an anterior fan of microtubules
attached to the anterior centriole).
The lower ones show the single plasma
membrane of unibacteria (posibacteria
plus archaebacteria), which were
ancestral to eukaryotes and the double
envelope of negibacteria, which were
ancestral to mitochondria and
chloroplasts (which retained the outer
membrane, red).
source: http://aob.oxfordjournals.org/cg
i/content/full/95/1/147/FIG2
[2] Fig. 1. A consensus phylogeny of
eukaryotes. The vast majority of
characterized eukaryotes, with the
notable exception of major subgroups of
amoebae, can now be assigned to one of
eight major groups. Opisthokonts (basal
flagellum) have a single basal
flagellum on reproductive cells and
flat mitochondrial cristae (most
eukaryotes have tubular ones).
Eukaryotic photosynthesis originated in
Plants; theirs are the only plastids
with just two outer membranes.
Heterokonts (different flagellae) have
a unique flagellum decorated with
hollow tripartite hairs (stramenopiles)
and, usually, a second plain one.
Cercozoans are amoebae with filose
pseudopodia, often living with in tests
(hard outer shells), some very
elaborate (foraminiferans). Amoebozoa
are mostly naked amoebae (lacking
tests), often with lobose pseudopodia
for at least part of their life cycle.
Alveolates have systems of cortical
alveoli directly beneath their plasma
membranes. Discicristates have discoid
mitochondrial cristae and, in some
cases, a deep (excavated) ventral
feeding groove. Amitochondrial
excavates lack substantial molecular
phylogenetic support, but most have an
excavated ventral feeding groove, and
all lack mitochondria. The tree shown
is based on a consensus of molecular
(1-4) and ultrastructural (16, 17) data
and includes a rough indication of new
ciPCR ''taxa'' (broken black lines)
(7-11). An asterisk preceding the taxon
name indicates probable paraphyletic
group.
source: http://www.sciencemag.org/cgi/co
ntent/full/300/5626/1703
evolve now.
Ribosomal RNA shows Rhizaria
Phylum "Foraminifera" (also known as
"Granuloreticulosea") evolve now.
Forminifera are catagorized as amoeboid
because they have pseudopods.
The Foraminifera, or forams for short,
are a large group of amoeboid protists
with reticulating pseudopods, fine
strands that branch and merge to form a
dynamic net. They typically produce a
shell, or test, which can have either
one or multiple chambers, some becoming
quite elaborate in structure. About 250
000 species are recognized, both living
and fossil. They are usually less than
1 mm in size, but some are much larger,
and the largest recorded specimen
reached 19 cm. As fossils, foraminifera
are extremely useful.
Foraminifera are
haplodiploid.
Most have a kind of shell
called a "test", which is composed of
calcium carbonate.
move by pseudopodia
most are marine
test
s are major components of limestone
used
to date marine sediments.
Foraminifera, especially the calcareous
forms, have a fossil record stretching
back to the Cambrian (Lee, 1990), and
are especially important
biostratigraphically.
b. Foraminiferans have a
multi-chambered CaCO3 (calcium
carbonate) shell; thin pseudopods
extend through holes.
Of the approximately 4000 living
species of foraminifera the life cycles
of only 20 or so are known. There are a
great variety of reproductive, growth
and feeding strategies, however the
alternation of sexual and asexual
generations is common throughout the
group and this feature differentiates
the foraminifera from other members of
the Granuloreticulosea. An asexually
produced haploid generation commonly
form a large proloculus (initial
chamber) and are therefore termed
megalospheric. Sexually produced
diploid generations tend to produce a
smaller proloculus and are therefore
termed microspheric. Importantly in
terms of the fossil record, many
foraminiferal tests are either
partially dissolved or partially
disintegrate during the reproductive
process.The planktonic foraminifera
Hastigerina pelagica reproduces by
gametogenesis at depth, the spines,
septa and apertural region are resorbed
leaving a tell-tale test.
Globigerinoides sacculiferproduces a
sac-like final chamber and additional
calcification of later chambers before
dissolution of spines occurs, this
again produces a distinctive test,
which once gametogenesis is complete
sinks to the sea bed. Since the
meiosis products have to differentiate
or mature into gametes, meiosis does
not result directly in gametes, these
species are haplodipoid
(haplodiplontic).
Modern forams are primarily marine,
although they can survive in brackish
conditions. A few species survive in
fresh water (e.g. Lake Geneva) and one
species even lives in damp rainforrest
soil. They are very common in the
meiobenthos, and about 40 species are
planktonic. The cell is divided into
granular endoplasm and transparent
ectoplasm. The pseudopodial net may
emerge through a single opening or many
perforations in the test, and
characteristically has small granules
streaming in both directions.
The pseudopods are used for locomotion,
anchoring, and in capturing food, which
consists of small organisms such as
diatoms or bacteria. A number of forms
have unicellular algae as
endosymbionts, from diverse lineages
such as the green algae, red algae,
golden algae, diatoms, and
dinoflagellates. Some forams are
kleptoplastic, retaining chloroplasts
from ingested algae to conduct
photosynthesis.
The foraminiferan life-cycle involves
an alternation between haploid and
diploid generations, although they are
mostly similar in form. The haploid or
gamont initially has a single nucleus,
and divides to produce numerous
gametes, which typically have two
flagella. The diploid or schizont is
multinucleate, and after meiosis
fragments to produce new gamonts.
Multiple rounds of asexual reproduction
between sexual generations is not
uncommon.
The form and composition of the test is
the primary means by which forams are
identified and classified. Most have
calcareous tests, composed of calcium
carbonate, which generally takes the
form of interlocking microscopic
crystals, giving it a glassy or hyaline
appearance. In other forams the test
may be composed of organic material,
made from small pieces of sediment
cemented together (agglutinated), and
in one genus of silica. Openings in the
test, including those that allow
cytoplasm to flow between chambers, are
called apertures.
Tests are known as fossils as far back
as the Cambrian period, and many marine
sediments are composed primarily of
them. For instance, the nummulitic
limestone that makes up the pyramids of
Egypt is composed almost entirely of
them. Forams may also make a
significant contribution to the overall
deposition of calcium carbonate in
coral reefs.
Because of their diversity, abundance,
and complex morphology, fossil
foraminiferal assembleages can give
accurate relative dates for rocks and
thus are extremely useful in
biostratigraphy. Before more modern
techniques became available, the oil
industry relied heavily on microfossils
such as foraminifera to find potential
oil deposits.
For the same reasons they make good
biostratigraphic markers, living
foraminiferal assembleages have been
used as bioindicators in coastal
environments, including as indicators
of coral reef health.
Fossil foraminifera are also useful in
paleoclimatology and paleoceanography.
They can be used to reconstruct past
climate by examining their oxygen
stable isotope ratios. Geographic
patterns seen in the fossil record of
planktonic forams are also used to
reconstruct paleo ocean current
patterns.
Genetic studies have identified the
naked amoeba Reticulomyxa and the
peculiar xenophyophores as
foraminiferans without tests. A few
other ameoboids produce reticulose
pseudopods, and were formerly
classified with the forams as the
Granuloreticulosa, but this is no
longer considered a natural group, and
most are now placed among the Cercozoa.
Both the Cercozoa and Radiolaria are
close relatives of the Foraminifera,
together making up the Rhizaria, but
the exact position of the forams is
still unclear.
PHYLUM Foraminifera
CLASS Athalamea (Haeckel,
1862)
CLASS Xenophyophorea (F.E.
Schulze, 1904)
CLASS Foraminifera
(Lee, 1990)
CLASS Foraminifera
ORDER Allogromiida
The
Allogromiida are a small group of
foraminiferans, including those that
produce organic tests (Lagynacea).
Genetic studies have shown that some
foraminiferans with agglutinated tests,
previously included in the Textulariida
or as their own order Astrorhizida,
also belong here. Allogromiids produce
relatively simple tests, usually with a
single chamber, similar to those of
other protists such as Gromia. They are
found in stressed environments,
including both marine and freshwater
forms, and are the oldest forams known
from the fossil record.
ORDER
Fusulinida
The fusulinids are an extinct group of
foraminiferan protozoa. They produce
calcareous shells, which are of fine
calcite granules packed closely
together; this distinguishes them from
other calcareous forams, where the test
is usually hyaline. Fusulinids are
important indicator fossils.
ORDER
Globigerinida
The Globigerinida are a common group of
foraminiferans that are found as marine
plankton (other groups are primarily
benthic). They produce hyaline
calcareous tests, and are known as
fossils from the Jurassic period
onwards. The group has included more
than 100 genera and over 400 species,
of which about 30 species are extant.
One of the most important genera is
Globigerina; vast areas of the ocean
floor are covered with Globigerina ooze
(named by Murray and Renard in 1873),
dominated by the shells of planktonic
forams.
ORDER Miliolida
The miliolids are a
group of foraminiferans, abundant in
shallow waters such as estuaries and
coastlines, though they also include
oceanic forms. They are distinguished
by producing porcelaneous tests,
composed of calcite needles and organic
material; the needles have a high
proportion of magnesium and are
oriented randomly. The test lacks pores
and generally has multiple chambers,
which are often arranged in a
distinctive fashion called milioline.
ORDER Rotaliida
The Rotaliida are a large and
abundant group of foraminiferans. They
are primarily oceanic benthos, although
some are common in shallower waters
such as estuaries. They also include
many important fossils, such as
nummulites. Rotaliids produce hyaline
tests, in which the microscopic
crystals may be oriented either
radially (as in other forams) or
obliquely.
ORDER Textulariida
The Textulariida are
a group of common foraminiferans that
produce agglutinated shells, composed
of foreign particles in an organic or
calcareous cement. Previously they were
taken to include all such species, but
genetic studies have shown that they
are not all closely related, and
several superfamilies have been moved
to the order Allogromiida. The
remaining forms are sometimes divided
into three orders: the Trochamminida
and Lituolida (organic cement) and the
Textulariida sensu stricto (calcareous
cement). All three are known as fossils
from the Cambrian onwards.
CLASS Xenophyophorea
Xenophyophores are marine
protozoans, giant single-celled
organisms found throughout the world's
oceans, but in their greatest numbers
on the abyssal plains of the deep
ocean. They were first described as
sponges in 1889, then as testate
amoeboids, and later as their own
phylum of Protista. A recent genetic
study suggested that the xenophyophores
are a specialized group of
Foraminifera. There are approximately
42 recognized species in 13 genera and
2 orders; one of which, Syringammina
fragillissima, is among the largest
known protozoans at a maximum 20
centimetres in diameter.
Abundant but poorly understood,
xenophyophores are delicate organisms
with a variable appearance; some may
resemble flattened discs, angular
four-sided shapes (tetrahedra), or like
frilly or spherical sponges. Local
environmental conditions-such as
current direction and speed-may play a
part in influencing these forms.
Xenophyophores are essentially lumps of
viscous fluid called cytoplasm
containing numerous nuclei distributed
evenly throughout. Everything is
contained in a ramose system of tubes
called a granellare, itself composed of
an organic cement-like substance.
As benthic deposit feeders,
xenophyophores tirelessly root through
the muddy sediments on the sea floor.
They excrete a slimy substance whilst
feeding; in locations with a dense
population of xenophyophores, such as
at the bottoms of oceanic trenches,
this slime may cover large areas. Local
population densities may be as high as
2,000 individuals per 100 square
metres, making them dominant organisms
in some areas. These giant protozoans
seem to feed in a manner similar to
amoebas, enveloping food items with a
foot-like structure called a
pseudopodium. Most are epifaunal
(living atop the seabed), but one
species (Occultammina profunda), is
known to be infaunal; it buries itself
up to 6 cm deep into the sediment.
Their glue-like secretions cause silt
and strings of their own fecal matter,
called stercomes, to build up into
masses (called stercomares) on their
exteriors. In this way, the organisms
form structures which project from the
sea floor; this characteristic also
explains their name, which may be
translated from the Greek to mean
"bearer of foreign bodies". A
protective, shell-like test is thereby
agglutinated around the granellare,
which is composed of scavenged minerals
and the microscopic skeletal remains of
other organisms, such as sponges,
radiolarians, and other foraminiferans.
Xenophyophores may be an important part
of the benthic ecosystem by virtue of
their constant bioturbation of the
sediments, providing a habitat for
other organisms such as isopods.
Research has shown that areas dominated
by xenophyophores have 3-4 times the
number of benthic crustaceans,
echinoderms, and molluscs than
equivalent areas which lack
xenophyophores. The xenophyophores
themselves also play commensal host to
a number of organisms-such as isopods
(e.g., genus Hebefustis), sipunculan
and polychaete worms, nematodes, and
harpacticoid copepods-some of which may
take up semi-permanent residence within
a xenophyophore's test. Brittle stars
(Ophiuroidea) also appear to have some
sort of relationship with
xenophyophores, as they are
consistently found directly underneath
or on top of the protozoans.
Xenophyophores are difficult to study
due to their extreme fragility.
Specimens are invariably damaged during
sampling, rendering them useless for
captive study or cell culture. For this
reason, very little is known of their
life history. As they occur in all the
world's oceans and in great numbers,
xenophyophores could be indispensable
agents in the process of sediment
deposition and in maintaining
biological diversity in benthic
ecosystems.
Xenophyophores are large marine Amoebae
containing barite (BaSO4) crystals.
CLASS Athalamea
Granuloreticulosea, lacking a
test or shell, though some forms might
be covered by a thin lorica. Pseudopods
could arise anywhere over the surface
of the body, and could be branched to a
greater or lesser extent in different
representa-tives of the group, with or
without anastomosing connections in the
pseudopodial network. Organisms that
have not been examined by modern
techniques, nor have been seen in
recent years, to check the fact that
they do have granular reticulopodial
bidirectional streaming, have been
removed from this class and placed with
the amoebae of uncertain affinities.
One genus remains: Reticulomyxa.
[1] FIG. 2. The tree of life based on
molecular, ultrastructural and
palaeontological evidence. Contrary to
widespread assumptions, the root is
among the eubacteria, probably within
the double-enveloped Negibacteria, not
between eubacteria and archaebacteria
(Cavalier-Smith, 2002b); it may lie
between Eobacteria and other
Negibacteria (Cavalier-Smith, 2002b).
The position of the eukaryotic root has
been nearly as controversial, but is
less hard to establish: it probably
lies between unikonts and bikonts (Lang
et al., 2002; Stechmann and
Cavalier-Smith, 2002, 2003). For
clarity the basal eukaryotic kingdom
Protozoa is not labelled; it comprises
four major groups (alveolates, cabozoa,
Amoebozoa and Choanozoa) plus the small
bikont phylum Apusozoa of unclear
precise position; whether Heliozoa are
protozoa as shown or chromists is
uncertain (Cavalier-Smith, 2003b).
Symbiogenetic cell enslavement occurred
four or five times: in the origin of
mitochondria and chloroplasts from
different negibacteria, of
chromalveolates by the enslaving of a
red alga (Cavalier-Smith, 1999, 2003;
Harper and Keeling, 2003) and in the
origin of the green plastids of
euglenoid (excavate) and chlorarachnean
(cercozoan) algae-a green algal cell
was enslaved either by the ancestral
cabozoan (arrow) or (less likely) twice
independently within excavates and
Cercozoa (asterisks) (Cavalier-Smith,
2003a). The upper thumbnail sketch
shows membrane topology in the
chimaeric cryptophytes (class
Cryptophyceae of the phylum Cryptista);
in the ancestral chromist the former
food vacuole membrane fused with the
rough endoplasmic reticulum placing the
enslaved cell within its lumen (red) to
yield the complex membrane topology
shown. The large host nucleus and the
tiny nucleomorph are shown in blue,
chloroplast green and mitochondrion
purple. In chlorarachneans (class
Chlorarachnea of phylum Cercozoa) the
former food vacuole membrane remained
topologically distinct from the ER to
become an epiplastid membrane and so
did not acquire ribosomes on its
surface, but their membrane topology is
otherwise similar to the cryptophytes.
The other sketches portray the four
major kinds of cell in the living world
and their membrane topology. The upper
ones show the contrasting ancestral
microtubular cytoskeleton (ciliary
roots, in red) of unikonts (a cone of
single microtubules attaching the
single centriole to the nucleus, blue)
and bikonts (two bands of microtubules
attached to the posterior centriole and
an anterior fan of microtubules
attached to the anterior centriole).
The lower ones show the single plasma
membrane of unibacteria (posibacteria
plus archaebacteria), which were
ancestral to eukaryotes and the double
envelope of negibacteria, which were
ancestral to mitochondria and
chloroplasts (which retained the outer
membrane, red).
source: http://aob.oxfordjournals.org/cg
i/content/full/95/1/147/FIG2
[2] Fig. 1. A consensus phylogeny of
eukaryotes. The vast majority of
characterized eukaryotes, with the
notable exception of major subgroups of
amoebae, can now be assigned to one of
eight major groups. Opisthokonts (basal
flagellum) have a single basal
flagellum on reproductive cells and
flat mitochondrial cristae (most
eukaryotes have tubular ones).
Eukaryotic photosynthesis originated in
Plants; theirs are the only plastids
with just two outer membranes.
Heterokonts (different flagellae) have
a unique flagellum decorated with
hollow tripartite hairs (stramenopiles)
and, usually, a second plain one.
Cercozoans are amoebae with filose
pseudopodia, often living with in tests
(hard outer shells), some very
elaborate (foraminiferans). Amoebozoa
are mostly naked amoebae (lacking
tests), often with lobose pseudopodia
for at least part of their life cycle.
Alveolates have systems of cortical
alveoli directly beneath their plasma
membranes. Discicristates have discoid
mitochondrial cristae and, in some
cases, a deep (excavated) ventral
feeding groove. Amitochondrial
excavates lack substantial molecular
phylogenetic support, but most have an
excavated ventral feeding groove, and
all lack mitochondria. The tree shown
is based on a consensus of molecular
(1-4) and ultrastructural (16, 17) data
and includes a rough indication of new
ciPCR ''taxa'' (broken black lines)
(7-11). An asterisk preceding the taxon
name indicates probable paraphyletic
group.
source: http://www.sciencemag.org/cgi/co
ntent/full/300/5626/1703
fossils.
These fossils are reported to be both
in Chuanlinggou Formation, China and in
Russia.
Acritarchs, the name coined by Evitt in
1963 which means "of uncertain origin",
are an artificial group. The group
includes any small (most are between
20-150 microns across), organic-walled
microfossil which cannot be assigned to
a natural group. They are characterised
by varied sculpture, some being spiny
and others smooth. They are believed to
have algal affinities, probably the
cysts of planktonic eukaryotic algae.
They are valuable Proterozoic and
Palaeozoic biostratigraphic and
palaeoenvironmental tools.
Chitinozoa
are large (50-2000 microns)
flask-shaped palynomorphs which appear
dark, almost opaque when viewed using a
light microscope. They are important
Palaeozoic microfossils as
stratigraphic markers.
The oldest known Acritarchs are
recorded from shales of
Palaeoproterozoic (1900-1600 Ma) age in
the former Soviet Union. They are
stratigraphically useful in the Upper
Proterozoic through to the Permian.
From Devonian times onwards the
abundance of acritarchs appears to have
declined, whether this is a reflection
of their true abundance or the volume
of scientific research is difficult to
tell.
[1] Figure 1 Protistan microfossils
from the Roper Group. a, c, Tappania
plana, showing asymmetrically
distributed processes and bulbous
protrusions (arrow in a). b, detail of
a, showing dichotomously branching
process. d, Valeria lophostriata. e,
Dictyosphaera sp. f, Satka favosa. The
scale bar in a is 35 µm for a and c;
10 µm for b; 100 µm for d; 15 µm for
e; and 40 µm for f.
source: Nature 412
[2] Diagram showing basic
morphological classification of
acritarchs. COPYRIGHTED
source: http://www.ucl.ac.uk/GeolSci/mic
ropal/acritarch.html
fossil Grypania spiralis (an alga 10 cm
long) from BIF in Michigan. Oldest
algae fossil.
The date of this fossil
was originally 2100mybn, but Schneider
measured the Marquette Range Supergroup
(MRS), A rhyolite in the Hemlock
Formation, a mostly bimodal submarine
volcanic deposit that is laterally
correlative with the Negaunee
Iron-formation, yields a sensitive
high-resolution ion microprobe (SHRIMP)
U-Pb zircon age of 1874 ± 9 Ma.
In 1992, Han and Runnegar, finders of
this fossil, compared the fossil to
Acetabularia, a single-celled green
algae. If true, this would make
Grypania the oldest green algae fossil.
source: file:/root/web/Grypania_spiralis
_wmel0000.htm
source: http://www.peripatus.gen.nz/pale
ontology/lrgGrypaniaspiralis.jpg
shows the archaebacteria and eukaryote
line separating here at 1,870 mybn
(first eukaryote, and first protist).
Rocks.
source:
shows Gram-negative and Gram-positive
eubacteria here at 1,584 mybn (first
Gram-positive bacteria).
relationship with cyanobacteria, which
form plastids (chloroplasts). Like
mitochondria, these organelles copy
themselves and are not made by the cell
DNA.
Depending on their morphology and
function, plastids are commonly
classified as chloroplasts,
leucoplasts, amyloplasts or
chromoplasts.
Genetic comparison
shows fungi evolving now. This begins
the fungi kingdom. Perhaps fungi
evolved from the amoebozoa slime mold
line, because the sporangiophore
(stalk) and sporangium (ball on top) of
slime molds look very similar to many
fungi.
to glaucophytes) evolves.
Ribosomal RNA place
first plant (single cell, similar to
glaucophytes) evolving here. This
begins the plant kingdom.
Cavelier-Smith and Ema E. -Y. Chao
write: "Kingdom Plantae
(sensuCavalier-Smith 1981) was
originally defined as comprising all
eukaryotes with chloroplasts possessing
an envelope of two membranes and
mitochondria with (irregularly) flat
cristae. It originally included
Viridaeplantae (green algae and
embryophyte or "higher" plants),
Rhodophyta (red algae), and Glaucophyta
(e.g., Cyanophora, Glaucocystis). It
was argued that all three groups
diverged from a single primary
symbiogenetic origin of plastids
(Cavalier-Smith 1982). Both the
monophyly of plastids and that of
Glaucophyta and Plantae long met
unreasonably strong opposition because
of widespread false dogma that
symbiogenesis is easy and because the
three taxa usually do not group
together in 18S rRNA trees. Now,
however, derived features of all
plastids compared with cyanobacteria
and numerous molecular trees have led
to the acceptance of plastid monophyly
(Delwiche and Palmer 1998) and to the
monophyly of glaucophyte algae.
Furthermore, a sister relation between
red algae and Viridaeplantae is
strongly supported by concatenated
protein trees for nuclei (Moreira et
al. 2000; Baldauf et al. 2000) and
chloroplasts (Martin et al. 1998;
Turmel et al. 1999). The sister
relationship between them and
glaucophytes is convincingly, but
significantly more weakly, supported by
the same trees. Thus the case of
Plantae shows that arguments from
morphology and evolutionary
considerations of protein targeting
during symbiogenesis (Cavalier-Smith
2000b) gave the correct answer much
more rapidly than single-gene trees,
which still do not clearly group all
three taxa together. In all our trees
in the present study (and the recent
tree of Edgcomb et al. 2002),
Rhodophyta and Viridaeplantae are
sisters, but with weak support.
Glaucophyta wander aimlessly from one
place to another in different trees."
R
ibosomal RNA place first plant evolving
here, although glaucophytes, the
earliest living plants (for many
people) do not evolve until later.
microfossils.
Genetic comparison
shows Phylum Glaucophyta evolving at
this time.
Some people catagorize Glaucophyta
in the kingdom Plantae instead of
Protista, and label glaucophyta the
most ancient living plants.
The glaucophytes, also referred to as
glaucocystophytes or glaucocystids, are
a tiny group of freshwater algae. They
are distinguished mainly by the
presence of cyanelles, primitive
chloroplasts which closely resemble
cyanobacteria and retain a thin
peptidoglycan wall between their two
membranes.
It is thought that the green algae
(from which the higher plants evolved),
red algae and glaucophytes acquired
their chloroplasts from endosymbiotic
cyanobacteria. The other types of algae
received their chloroplasts through
secondary endosymbiosis, by engulfing
one of those types of algae along with
their chloroplasts.
The glaucophytes are of obvious
interest to biologists studying the
development of chloroplasts: if the
hypothesis that primary chloroplasts
had a single origin is correct,
glaucophytes are closely related to
both green plants and red algae, and
may be similar to the original alga
type from which all of these developed.
Glaucophytes have mitochondria with
flat cristae, and undergo open mitosis
without centrioles. Motile forms have
two unequal flagella, which may have
fine hairs and are anchored by a
multilayered system of microtubules,
both of which are similar to forms
found in some green algae.
The
chloroplasts of glaucophytes, like the
cyanobacteria and the chloroplasts of
red algae, use the pigment phycobilin
to capture some wavelengths of light;
the green algae and higher plants have
lost that pigment.
There are three main genera included
here. Glaucocystis is non-motile,
though it retains very short vestigial
flagella, and has a cellulose wall.
Cyanophora is motile and lacks a cell
wall. Gloeochaete has both motile and
non-motile stages, and has a cell wall
that does not appear to be composed of
cellulose.
DOMAIN Eukaryota - eukaryotes
KINGDOM Plantae
Haeckel, 1866 - plants
SUBKINGDOM Biliphyta
Cavalier-Smith, 1981
PHYLUM Glaucophyta
Skuja, 1954
CLASS Glaucocystophyceae
Schaffner, 1922
[1] ? COPYRIGHTED
source: http://protist.i.hosei.ac.jp/PDB
3/PCD3711/htmls/86.html
[2] ? COPYRIGHTED
source: http://protist.i.hosei.ac.jp/PDB
/Images/Others/Glaucocystis/
evolve from Unikonts (ancestrally only
one cilium). Opisthokonts have flat
mitochondrial cristae and go on to form
the Animal and Fungi kingdoms.
Thomas
Cavalier-Smith and Ema E.-Y. Chao
write: "The term opisthokont,
signifying "posterior cilium," was
applied to animals, Choanozoa, and
Fungi because all three groups
ancestrally had a single posterior
cilium (Cavalier-Smith 1987b). They
were argued to be a clade because they
also were characterized (uniquely at
the time) by flat, nondiscoid
mitochondrial cristae that were not
irregularly inflated like the flat
cristae of Plantae (Cavalier-Smith
1987b). Four other characters also
suggested that animals and fungi were
more closely related to each other than
plants (chitinous exoskeletons; storage
of glycogen, not starch; absence of
chloroplasts; and UGA coding for
tryptophane, not chain termination).
However, the first three were probably
ancestral states for eukaryotes and the
last convergent, so the ciliary and
cristal morphology were stronger
indications. Although early rRNA trees
did not group animals and fungi
together, the opisthokonts are now
consistently supported by all
well-sampled rRNA trees and trees using
several or many proteins, as discussed
above. Moreover a derived 12-amino acid
insertion in translation elongation
factor 1agr and three small gaps in
enolase clearly indicate that animals
and fungi have a common ancestor not
shared with plants (or other bikonts)
or Amoebozoa (Baldauf and Palmer 1993;
Baldauf 1999). Thus opisthokonts are
now well accepted as a robust clade of
eukaryotes (Patterson 1999)."
[1] cavalier-smith diagram COPYRIGHTED
source: cavalier_jmolevol_2003_56_540-56
3.pdf
[2] Figure 1. Phylogenetic hypothesis
of the eukaryotic lineage based on
ultrastructural and molecular data.
Organisms are divided into three main
groups distinguished by mitochondrial
cristal shape (either discoidal,
flattened or tubular). Unbroken lines
indicate phylogenetic relationships
that are firmly supported by available
data; broken lines indicate
uncertainties in phylogenetic
placement, resolution of which will
require additional data. Color coding
of organismal genus names indicates
mitochondrial genomes that have been
completely (Table 1), almost completely
(Jakoba, Naegleria and
Thraustochytrium) or partially (*)
sequenced by the OGMP (red), the FMGP
(black) or other groups (green). Names
in blue indicate those species whose
mtDNAs are currently being sequenced by
the OGMP or are future candidates for
complete sequencing. Amitochondriate
retortamonads are positioned at the
base of the tree, with broken arrows
denoting the endosymbiotic origin(s) of
mitochondria from a Rickettsia-like
eubacterium. Macrophar.,
Macropharyngomonas.
source: unknown
evolve now.
Ribosomal RNA shows the Protist
Phylum Amoebozoa (also called
Ramicristates) which includes amoeba
and slime molds evolving now.
The Amoebozoa are a major group of
amoeboid protozoa, including the
majority that move by means of internal
cytoplasmic flow. Their pseudopodia are
characteristically blunt and
finger-like, called lobopodia. Most are
unicellular, and are common in soils
and aquatic habitats, with some found
as symbiotes of other organisms,
including several pathogens. The
Amoebozoa also include the slime
moulds, multinucleate or multicellular
forms that produce spores and are
usually visible to the unaided eye.
Mycetozoa are the slime molds.
4. Plasmodial
Slime Molds
a. Plasmodial
slime molds exist as a plasmodium. (the
earlier evolved acrasid cellular slime
molds exist as individual amoeboid
cells.)
b. This diploid
multinucleated cytoplasmic mass creeps
along, phagocytizing decaying plant
material.
c. Fan-shaped plasmodium
contains tubules of concentrated
cytoplasm in which liquefied cytoplasm
streams.
d. Under unfavorable
environmental conditions (e.g.,
drought), the plasmodium develops many
sporangia
that produce spores by
meiosis.
e. When mature, spores are
released and survive until more
favorable environmental conditions
return;
then each releases a
haploid flagellated cell or an amoeboid
cell.
f. Two flagellated or
amoeboid cells fuse to form diploid
zygote that produces a multi-nucleated
plasmodium.
Nuclear division in giant amoebas
(Peolobiont/Amoebozoa) is neither
mitosis nor binary fission, but
incorporates aspects of both (Fig.
3-7). Chromosomes are attached
permanently to the nuclear membrane by
their centromeres (MTOCs, microtubule
organizing centers), and the nuclear
membrane remains intact throughout
division. After DNA duplication
produces two chromatids, the point of
attachment, the MTOC duplicates or
divides, and microtubules are assembled
between the two resulting MTOCs.
Elongating microtubules form something
akin to a spindle within the nuclear
membrane that pushes the daughter
chromosomes apart and elongate the
membrane-bounded nucleus until it blebs
in half in something akin to binary
fission. Simple assembly of
microtubules accomplishes the
separation of daughter genomes in this
simple nuclear division. In typical
eukaryotic mitosis, the separation of
daughter chromosomes is accomplished by
a dual action, the disassembly of
spindle fibers connecting the daughter
chromosome to the polar MTOC, and
assembly of spindle fibers running pole
to pole.
amoeba haplodiploid?
Thomas Cavalier-Smith and Ema
E. -Y. Chao write: "Amoebozoa are a key
protozoan phylum because of the
possibility that they are ancestrally
uniciliate and unicentriolar
(Cavalier-Smith 2000a,b); present data
on the DHFR-TS gene fusion leaves open
the possibility that they might be the
earliest-diverging eukaryotes
(Stechmann and Cavalier-Smith 2002),
but they may be evolutionarily closer
to bikonts or even opisthokonts.
Amoebozoa comprise two subphyla
(Cavalier-Smith 1998a): Lobosa,
classical aerobic amoebae with broad
("lobose") pseudopods (including the
testate Arcellinida), and Conosa (slime
molds {Mycetozoa, e.g., Dictyostelium}
and amitochondrial-often
uniciliate-archamaebae {entamoebae,
mastigamoebae}). Contrary to early
analyses (Sogin 1991; Cavalier-Smith
1993a), there is no reason to regard
Amoebozoa as polyphyletic; the defects
of those classical uncorrected rRNA
trees are shown by trees using 123
proteins that robustly establish the
monophyly of both Archamoebae and
Conosa (Bapteste et al. 2002). Unless
the tree's root is within Conosa,
Dictyostelium and Entamoeba must have
evolved independently from aerobic
flagellates by ciliary losses. A recent
mitochondrial gene tree based on
concatenating six different proteins
grouped Dictyostelium with Physarum
(99% support) and both Mycetozoa as
sisters to Acanthamoeba (99% support),
thus providing strong evidence for the
monophyly of Mycetozoa and the grouping
of Lobosa and Conosa as Amoebozoa
(Forget et al. 2002)-the same tree also
strongly supports the idea based on
morphology that Allomyces should be
excluded from Chytridiomycetes (in the
separate class Allomycetes) and is
phylogenetically closer to zygomycetes
and higher fungi (Cavalier-Smith 1998a,
2000c). Furthermore, the derived gene
fusion between two cytochrome oxidase
genes, coxI and coxII (Lang et al.
1999), strongly supports the holophyly
of Mycetozoa. Since Archamoebae
secondarily lost mitochondria, the root
cannot lie among them either-although
anaerobiosis in Archamoebae is derived,
it is unjustified to conclude from this
that their simple ciliary root
organization, which was a key reason
for considering them early eukaryotes
(Cavalier-Smith 1991c), is also
secondarily derived (Edgcomb et al.
2002). Thus the root of the eukaryote
tree cannot lie within the Conosa.
As Mycetozoa and Archamoebae have very
long-branch rRNA sequences, Conosa were
excluded from the analysis in Fig. 1,
which includes only Lobosa. Although
the monophyly of Acanthamoebida (99%)
and of Euamoebida (85%) is well
supported, the basal branching of the
Lobosa is so poorly resolved that the
monophyly of Lobosa might appear open
to question. The four lobosan lineages
apparently diverged early. However, in
the 279- and 227-species trees, which
included Conosa, anaeromonads did not
intrude into the Amoebozoa as they do
in Fig. 1, and Amoebozoa were
monophyletic (low support) except for
the exclusion of M. invertens. M.
invertens is another wandering branch,
which in some taxon sample/methods
groups very weakly with other
Amoebozoa, but more often ends up in a
different place in each tree! We concur
with the judgment of Milyutina et al.
(2001)Edgcomb et al. (2002) that it
should not be regarded as a pelobiont
or Archamoeba, but as a lobosan that
independently became an anaerobe with
degenerate mitochondria. Its tendency
to drift around the tree, coupled with
its short branch, suggests that it may
be a particularly early-diverging
amoebozoan lineage. If so, its
unicentriolar condition would give
added support to the idea that
Amoebozoa are ancestrally uniciliate,
if it could be shown that Amoebozoa are
either holophyletic or not at the base
of the tree.
Most, if not all, amoebae evolved from
amoeboid zooflagellates by multiple
ciliary losses (Cavalier-Smith 2000a).
As the uniciliate condition is
widespread within Amoebozoa
(Cavalier-Smith 2000a, 2002b), it may
be their ancestral condition; if so,
ordinary nonciliate amoebozoan amoebae
arose several times independently.
Evolution of amoebae from
zooflagellates by ciliary loss also
occurred separately in Choanozoa to
produce Nuclearia and in several bikont
groups, notably Percolozoa
(heterolobosean amoebae, e.g.,
Vahlkampfia) and Cercozoa. However, we
cannot currently exclude the
possibility that the eukaryote tree is
rooted within the lobosan Amoebozoa, in
which case one of its nonciliate
lineages (Euamoebida or Vanellidae)
might be primitively nonciliate and the
earliest-diverging eukaryotic lineage.
However, as the idea that the nucleus
and a single centriole and cilium
coevolved in the ancestral eukaryote
(Cavalier-Smith 1987a) retains its
theoretical merits, we think it more
likely that all Amoebozoa are derived
from a uniciliate ancestor and that
crown Amoebozoa are a clade."
Amoebozoa vary greatly in size. Many
are only 10-20 μm in size, but
they also include many of the larger
protozoa. The famous species Amoeba
proteus may reach 800 μm in
length, and partly on account of its
size is often studied as a
representative cell. Multinucleate
amoebae like Chaos and Pelomyxa may be
several millimetres in length, and some
slime moulds cover several square feet.
The cell is typically divided into a
granular central mass, called
endoplasm, and a clear outer layer,
called ectoplasm. During locomotion the
endoplasm flows forwards and the
ectoplasm runs backwards along the
outside of the cell. Many amoebae move
with a definite anterior and posterior;
in essence the cell functions as a
single pseudopod. They usually produce
numerous clear projections called
subpseudopodia (or determinate
pseudopodia), which have a defined
length and are not directly involved in
locomotion.
Other amoebozoans may form multiple
indeterminate pseudopodia, which are
more or less tubular and are mostly
filled with granular endoplasm. The
cell mass flows into a leading
pseudopod, and the others ultimately
retract unless it changes direction.
Subpseudopodia are usually absent. In
addition to a few naked forms like
Amoeba and Chaos, this includes most
amoebae that produce shells. These may
be composed of organic materials, as in
Arcella, or of collected particles
cemented together, as in Difflugia,
with a single opening through which the
pseudopodia emerge.
The primary mode of nutrition is by
phagocytosis: the cell surrounds
potential food particles, sealing them
into vacuoles where the may be digested
and absorbed. Some amoebae have a
posterior bulb called a uroid, which
may serve to accumulate waste,
periodically detaching from the rest of
the cell. When food is scarce, most
species can form cysts, which may be
carried aerially and introduce them to
new environments. In slime moulds,
these structures are called spores, and
form on stalked structures called
fruiting bodies or sporangia.
Most Amoebozoa lack flagella and more
generally do not form
microtubule-supported structures except
during mitosis. However, flagella occur
among the pelobionts, and many slime
moulds produce biflagellate gametes.
The flagella is generally anchored by a
cone of microtubules, suggesting a
close relationship to the opisthokonts.
The mitochondria characteristically
have branching tubular cristae, but
have been lost among pelobionts and the
parasitic entamoebids, collectively
referred to as archamoebae based on the
earlier assumption that the absence was
primitive.
Traditionally all amoebae with lobose
pseudopods were treated together as the
Lobosea, placed with other amoeboids in
the phylum Sarcodina or Rhizopoda, but
these were considered to be unnatural
groups. Structural and genetic studies
identified several independent groups:
the percolozoans, pelobionts, and
entamoebids. In phylogenies based on
rRNA their representatives were
separate from other amoebae, and
appeared to diverge near the base of
eukaryotic evolution, as did most slime
molds.
However, revised trees by
Cavalier-Smith and Chao in 1996
suggested that the remaining lobosans
do form a monophyletic group, and that
the archamoebae and Mycetozoa are
closely related to it, although the
percolozoans are not. Subsequently they
emended (to improve by editing) the
older phylum Amoebozoa to refer to this
supergroup. Studies based on other
genes have provided strong support for
the unity of this group. Patterson
treated most with the testate filose
amoebae as the ramicristates, based on
mitochondrial similarities, but the
latter are now removed to the Cercozoa.
Amoebae are difficult to classify, and
relationships within the phylum remain
confused. Originally it was divided
into the subphyla Conosa, comprising
the archamoebae and Mycetozoa, and
Lobosa, including the more typical
lobose amoebae. Molecular phylogenies
provide some support for this division
if the Lobosa are understood to be
paraphyletic. They also suggest the
morphological families of naked
lobosans may correspond at least partly
to natural groups:
* Leptomyxida
* Amoebidae
* Hartmannellidae
* Paramoebidae
*
Vannellidae
* Vexilliferidae
* Acanthamoebidae
* Stereomyxidae
However, many amoebae have not yet been
studied via molecular techniques,
including all those that produce shells
(Arcellinida).
PHYLUM Amoebozoa (Lühe, 1913 emend.)
Cavalier-Smith, 1998
CLASS
Breviatea
CLASS Variosea
CLASS Phalansterea (T. Cavalier-Smith,
2000)
SUBPHYLUM Lobosa (Carpenter,
1861) Cavalier-Smith, 1997 (lobose
amoebas)
CLASS Amoebaea
CLASS
Testacealobosea (includes shelled
lobosid amebas {testate amoebas})
CLASS
Holomastigea T. Cavalier-Smith, 1997
("1996-1997")
SUBPHYLUM Conosa
(Cavalier-Smith, 1998)
INTRAPHYLUM
Mycetozoa (De Bary, 1859)
Cavalier-Smith, 1998 (Slime Molds)
SUPERCLASS Eumyxa (Cavalier-Smith,
1993) Cavalier-Smith, 1998
CLASS
Protostelea (C.J. Alexopoulos & C.W.
Mims, 1979 orthog. emend.)
CLASS Myxogastrea (E.M. Fries, 1829
stat. nov. J. Feltgen, 1889 orthog.
emend.) (plasmodial slime molds)
SUPERCLASS Dictyostelia (Lister, 1909)
Cavalier-Smith, 1998
CLASS
Dictyostelea (D.L. Hawksworth et
al., 1983, orthog. emend.)
INTRAPHYLUM Archamoebae
(Cavalier-Smith, 1983) Cavalier-Smith,
1998
CLASS Pelobiontea (F.C. Page,
1976 stat. nov. T. Cavalier-Smith,
1981)
CLASS Entamoebea (T.
Cavalier-Smith, 1991)
SUBPHYLUM Lobosa
SUBPHYLUM Conosa
The Conosea unifies amoebae
which usually possess flagellate stages
or are amoeboflagellates. This clade
consists of two relatively solid groups
� the Mycetozoa and Archamoebae,
grouped by Cavalier-Smith (1998) in the
taxon Conosa, as well as a number of
independent lineages, including two
flagellates � Phalansterium
(Cavalier-Smith et al. 2004) and
Multicilia (Nikolaev et al. 2004), and
two gymnamoebae � Gephyramoeba
and Filamoeba (Amaral Zettler et al.
2000). Because of large variations of
the substitution rates in SSU rRNA
genes within this clade, its internal
relationships are not resolved yet.
The Mycetozoa comprises two distinct
groups of �slime molds�
� the Myxogastria and
Protostelia (Dykstra and Keller 2000).
This is a well-defined group of
protists, characterized by the ability
to form so-called �fruiting
bodies�. In some lineages of
Mycetozoa the fruiting body is raised
over the substratum on a distinct
stalk. Both groups possess complex life
cycles including an aggregation of
cells, however the essential difference
between them is that in Protostelia,
only a pseudoplasmodium is formed
(without fusion of the cells
constituting the aggregate), while in
Myxogastria a true plasmodium is formed
(the cells completely fuse, forming a
single organism) (Olive 1975; Dykstra
and Keller 2000). The monophyly of
Mycetozoa was proposed based on
elongation factor 1-alpha gene
sequences (Baldauf and Doolittle 1997)
but it is not always recovered in SSU
rRNA trees (Cavalier-Smith et al. 2004;
Nikolaev et al. 2004).
The Archamoebae comprise amoeboid and
amoeboflagellate protists characterized
by a secondary absence of mitochondria
(mostly due to parasitism or life in
anoxic environments). This group
includes the free-living genera
Mastigamoeba, Mastigella, and Pelomyxa
(the pelobionts) and the parasitic
genera Entamoeba and Endolimax (the
entamoebids). The consistent grouping
of all these amitochondriate amoeboid
organisms in both SSU rRNA and actin
gene phylogenies (Fahrni et al. 2003)
suggests a single loss of the
mitochondria during the evolution of
Amoebozoa.
CLASS Amoebaea
ORDER Euamoebida Lepsi, 1960
FAMILY Amoebidae (Ehrenberg 1838)
The
Amoebidae are a family of amoebozoa,
including naked amoebae that produce
multiple pseudopodia of indeterminate
length. These are roughly cylindrical
in form, with a central stream of
granular endoplasm, and do not have
subpseudopodia. During locomotion one
pseudopod typically becomes dominant,
and the others are retracted as the
body flows into it. In some cases the
cell moves by "walking", with the
relatively permanent pseudopodia
serving as limbs.
The most important genera are Amoeba
and Chaos, which are set apart from the
others by longitudinal ridges. They
group together on molecular trees,
suggesting the Amoebidae are a natural
group. Shelled amoebozoans have not
been studied molecularly but produce
very similar pseudopodia, so although
they are traditionally classified
separately they may be closely related
to this group.
GENUS Amoeba (Bery de St. Vincent 1822)
Amoeba (also spelled ameba) is a genus
of protozoa that moves by means of
temporary projections called
pseudopods, and is well-known as a
representative unicellular organism.
The word amoeba is variously used to
refer to it and its close relatives,
now grouped as the Amoebozoa, or to all
protozoa that move using pseudopods,
otherwise termed amoeboids.
Amoeba itself is found in freshwater,
typically on decaying vegetation from
streams, but is not especially common
in nature. However, because of the ease
with which they may be obtained and
kept in the lab, they are common
objects of study, both as
representative protozoa and to
demonstrate cell structure and
function. The cells have several lobose
pseudopods, with one large tubular
pseudopod at the anterior and several
secondary ones branching to the sides.
The most famous species, Amoeba
proteus, is 700-800 μm in length,
but many others are much smaller. Each
has a single nucleus, and a simple
contractile vacuole which maintains its
osmotic pressure, as its most
recognizable features.
Early naturalists referred to Amoeba as
the Proteus animalcule, after a Greek
god who could change his shape. The
name "amibe" was given to it by Bery
St. Vincent, from the Greek amoibe,
meaning change.
A good method of collecting amoeba is
to lower a jar upside down until it is
just above the sediment surface. Then
one should slowly let the air escape so
the top layer will be sucked into the
jar. Deeper sediment should not be
allowed to get sucked in. It is
possible to slowly move the jar when
tilting it to collect from a larger
area. If no amoeba are found, one can
try introducing some rice grains into
the jar and waiting for them to start
to rot. The bacteria eating the rice
will be eaten by the amoeba, thus
increasing the population and making
them easier to find.
Family Hartmannellidae (Volkonsky
1931)
The Hartmannellidae are a common family
of amoebozoa, usually found in soils.
When active they tend to be roughly
cylindrical in shape, with a single
leading pseudopod and no
subpseudopodia. This form somewhat
resembles a slug, and as such they are
also called limax amoebae. Trees based
on rRNA show the Hartmannellidae are
paraphyletic to the Amoebidae and
Leptomyxida, which may adopt similar
forms.
FAMILY Vannellidae (Bovee 1970)
The
Vannellidae are a distinctive family of
amoebozoa. During locomotion they tend
to be flattened and fan-shaped,
although some are long and narrow, and
have a prominent clear margin at the
anterior. In most amoebae, the
endoplasm glides forwards through the
center of the cell, but in vannellids
the cell undergoes a sort of rolling
motion, with the outer membrane sliding
around like a tank tread.
These amoebae are usually 10-40 μm
in size, but some are smaller or
larger. The most common genus is
Vannella, found mainly in soils, but
also in freshwater and marine habitats.
Trees based on rRNA support the
monophyly of the family.
SUBPHYLUM Conosa Cavalier-Smith, 1998
INTRAPHYLUM Archamoebae
(Cavalier-Smith, 1983) Cavalier-Smith,
1998
CLASS Pelobiontea F.C. Page, 1976
stat. nov. T. Cavalier-Smith, 1981
ORDER Pelobiontida (Page 1976)
The pelobionts
are a small group of amoebozoa. The
most notable member is Pelomyxa, a
giant amoeba with multiple nuclei and
inconspicuous non-motile flagella. The
other genera, called mastigamoebae, are
often uninucleate, have a single
anterior flagellum used in swimming,
and produce numerous determinate
pseudopodia.
Pelobionts are closely related to the
entamoebids and like them have no
mitochondria; in addition, pelobionts
also do not have dictyosomes. At one
point these absences were considered
primitive. However, molecular trees
place the two groups with other lobose
amoebae in the phylum Amoebozoa, so
these are secondary losses.
SUBPHYLUM Conosa Cavalier-Smith, 1998
INTRAPHYLUM Archamoebae
(Cavalier-Smith, 1983) Cavalier-Smith,
1998
CLASS Entamoebea T. Cavalier-Smith,
1991
The entamoebids or entamoebae are a
group of amoebozoa found as internal
parasites or commensals of animals. The
cells are uninucleate small, typically
10-100 μm across, and usually have
a single lobose pseudopod taking the
form of a clear anterior bulge. There
are two major genera, Entamoeba and
Endolimax. They include several species
that are pathogenic in humans, most
notably Entamoeba histolytica, which
causes amoebic dysentery.
Entamoebids lack mitochondria. This is
a secondary loss, possibly associated
with their parasitic life-cycle.
Studies show they are close relatives
of the pelobionts, another group of
amitochondriate amoebae, but unlike
them entamoebids retain dictyosomes.
Both groups are now placed alongside
other lobose amoebae in the phylum
Amoebozoa.
Studying Entamoeba invadens, David
Biron of the Weizmann Institute of
Science and coworkers found that about
one third of the cells are unable to
separate unaided and recruit a
neighboring amoeba (dubbed the
"midwife") to complete the fission. He
writes:
"When an amoeba divides, the two
daughter cells stay attached by a
tubular tether which remains intact
unless mechanically severed. If called
upon, the neighbouring amoeba midwife
travels up to 200 μm towards the
dividing amoeba, usually advancing in a
straight trajectory with an average
velocity of about 0.5 μm/s. The
midwife then proceeds to rupture the
connection, after which all three
amoebae move on."
They also reported a similar behavior
in Dictyostelium.
Entamoeba coli is a non-pathogenic
species of entamoebid that is important
clinically in humans only because it
can be confused with Entamoeba
histolytica, which is pathogenic, on
microscopic examination of stained
stool specimens. A simple finding of
Entamoeba coli trophozoites or cysts in
a stool specimen requires no treatment.
Entamoeba histolytica is an anaerobic
parasitic protozoan, classified as an
entamoebid. It infects predominantly
humans and other primates. Diverse
mammals such as dogs and cats can
become infected but usually do not shed
cysts (the environmental survival form
of the organism) with their feces, thus
do not contribute significantly to
transmission. The active (trophozoite)
stage exists only in the host and in
fresh feces; cysts survive outside the
host in water and soils and on foods,
especially under moist conditions on
the latter. When swallowed they cause
infections by excysting (to the
trophozoite stage) in the digestive
tract.
Endolimax nana, a small entamoebid that
is a commensal of the human intestine,
causes no known disease. It is most
significant in medicine because it can
provide false positives for other
tests, such as for the related species
Entamoeba histolytica which causes
amoebic dysentery, and because its
presence indicates that the host once
consumed feces. It forms cysts with
four nuclei which excyst in the body
and become trophozoites. Endolimax nana
nuclei have a large endosome somewhat
off-center and small amounts of visible
chromatin or none at all.
Actinopod reproduction may involve
binary fission or the formation of
swarmer cells, and sexual processes
occur in some groups. Their
mitochondrial cristae are usually
tubular, but in some groups there are
vesicular or flattened, plate-like
cristae.
[1] SUBPHYLUM Lobosa CLASS Amoebaea
Chaos diffluens, an amoeba. Photo
released by Dr. Ralf Wagner.
source: http://en.wikipedia.org/wiki/Ima
ge:Chaos_diffluens.jpg
[2] CLASS Amoebaea Mayorella
(may-or -ell-a) a medium sized
free-living naked amoeba with conical
pseudopodia. Central body is the
nucleus. Phase contrast. This picture
was taken by David Patterson of
material from Limulus-ridden sediments
at Plum Island (Massachusetts USA) in
spring and summer, 2001. NONCOMMERCIAL
USE
source: http://microscope.mbl.edu/script
s/microscope.php?func=imgDetail&imageID=
515
Phlya Chlorophyta (volvox, sea lettuce)
and Charophyta (Spirogyra) evolve.
Gene
tic comparison shows Green Algae,
composed of the 2 Phlya Chlorophyta
(volvox, sea lettuce) and Charophyta
(Spirogyra) evolving now.
The Green Algae are the large group of
algae from which the embryophytes
(higher plants) emerged. As such they
form a paraphyletic group, some people
placing them in the Plantae Kingdom,
while others placing them in the
Protist Kingdom.
Almost all forms have chloroplasts.
They are bound by a double membrane, so
presumably were acquired by direct
endosymbiosis of cyanobacteria.
All green algae have mitochondria with
flat cristae. When present flagella are
typically anchored by a cross-shaped
system of microtubules, but these are
absent among the higher plants and
charophytes. They usually have cell
walls containing cellulose, and undergo
open mitosis without centrioles. Sexual
reproduction varies from fusion of
identical cells (isogamy) to
fertilization of a large non-motile
cell by a smaller motile one (oogamy).
However, these traits show some
variation, most notably among the basal
green algae, called prasinophytes.
The first land plants most likely
evolved from green algae.
Here is where the green algae separate
from the ancestor of the first land
plants.
Spirogyra reproduce through
conjugation, which either was inherited
from prokaryotes or evolved a second
time in eukaryotes.
Some filamentous green algae (e.g.
cladophora) are haplodiploid (alternate
between haploid and diploid cycles that
both have mitosis).
1. Phylum Chlorophyta (green
algae) contains about 7,000 species.
2.
Most live in the ocean but are more
likely found in fresh water; they can
even be found on moist land.
3. Green
algae are believed to be closely
related to the first plants because
both of these groups
a. have a
cell wall that contains cellulose,
b.
possess chlorophylls a and b, and
c. store reserve food as starch
inside of the chloroplast.
4. Green algae
are not always green; some have
pigments that give them an orange, red,
or rust color.
5. Body organizations
include single cells, colonies,
filaments and multicellular forms.
C. Flagellated Green Algae
1.
Chlamydomonas is a unicellular green
alga less than 25 cm long. (Fig. 30.3)
2. It has a cell wall and a single,
large, cup-shaped chloroplast with a
pyrenoid for starch synthesis.
3. The
chloroplast contains a light-sensitive
eyespot (stigma) that directs the cell
to light for photosynthesis.
4. Two long
whip-like flagella project from the
anterior end to propel the cell toward
light.
5. When growth conditions are
favorable, Chlamydomonas reproduces
asexually with zoospores.
6. When growth
conditions are unfavorable,
Chlamydomonas reproduces sexually.
a.
Gametes from two different mating types
join to form a zygote.
b. A heavy
wall forms around the zygote; a
resistant zygospores survives until
conditions are favorable.
c. Some are
heterogametes similar to sperm and egg
that stores food, a condition called
oogamy.
d. In most, gametes are
identical, a condition called isogamy.
D. Filamentous Green Algae
1.
Cell division in one plane produces
end-to-end chains of cells or
filaments.
2. Spirogyra is a filamentous
algae found on surfaces of ponds and
streams.
a. It has ribbon-like
spiral chloroplasts. (Fig. 30.4)
b. Two strands may unite in conjugation
and exchange genetic material, forming
a diploid zygote.
c. The zygotes
withstand winter; in spring they
undergo meiosis to produce haploid
filaments.
3. Oedogonium is another
filamentous algae.
a. It has
cylindrical cells with netlike
chloroplasts.
b. During sexual
reproduction, there is a definite egg
and sperm.
E. Multicellular Green Algae
1.
Multicellular Ulva is called sea
lettuce because of its leafy
appearance. (Fig. 30.5)
2. The
thallus (body) is two cells thick but
can be a meter long.
3. Ulva has an
alternation of generations life cycle,
as do plants, but the generations look
alike.
4. The gametes look alike
(isogametes) and the spores are
flagellated.
5. In true plants, one
generation is dominant, sperm and eggs
are produced, and spores lack flagella.
F. Colonial Green Algae
1. Volvox
is a hollow sphere with thousands of
cells arranged in a single layer. (Fig.
30.6)
2. Volvox cells resembles
Chlamydomonas cells; a colony arises as
if daughter cells fail to separate.
3.
Volvox cells cooperate when flagella
beat in a coordinated fashion.
4. Some
cells are specialized forming a new
daughter colony within the parental
colony.
5. Daughter colonies are inside
a parent colony until an enzyme
dissolves part of a wall so it can
escape.
6. Sexual reproduction involves
oogamy
Order Chlorococcales, probably includes
the first coccoidal green algae,
probably even the earliest eukaryotes,
but unequivocal indentification in the
Precambrien is unlikely to be achived.
Spirogyra reproduce through
conjugation, which either was inherited
from prokaryotes or evolved a second
time in eukaryotes. If inherited from
prokaryotes, then spirogrya would be
very old although the fossil record and
Ribosomal RNA put them late compared to
other algae.
[1] Micrograph of Volvox aureus.
Copyright held by Dr. Ralf Wagner,
uploaded to German Wikipedia under
GFDL. Permission is granted to copy,
distribute and/or modify this document
under the terms of the GNU Free
Documentation License, Version 1.2 or
any later version published by the Free
Software Foundation; with no Invariant
Sections, no Front-Cover Texts, and no
Back-Cover Texts. Subject to
disclaimers.
source: http://en.wikipedia.org/wiki/Vol
vox
[2] Photo of green algal growth
(Enteromorpha sp.) on rocky areas of
the ocean intertidal shore, indicating
a nearby nutrient source (in this case
land runoff). Photographed by Eric
Guinther near Kahuku, O'ahu,
Hawai'i. GFDL Permission is granted
to copy, distribute and/or modify this
document under the terms of the GNU
Free Documentation License, Version 1.2
or any later version published by the
Free Software Foundation; with no
Invariant Sections, no Front-Cover
Texts, and no Back-Cover Texts Subject
to disclaimers
source: http://en.wikipedia.org/wiki/Ima
ge:Intertidal_greenalgae.jpg
Gene
tic comparison show Phylum Rhodophyta
(red algae) evolves now.
There are between 2500 and 6000 species
in about 670 largely marine genera.
Many red algae are haplodiploid
(alternate between haploid and diploid
cycles that both have mitosis).
The red algae (Rhodophyta) are a large
group of mostly multicellular, marine
algae, including many notable seaweeds.
Most of the coralline algae, which
secrete calcium carbonate and play a
major role in building coral reefs,
belong here. Red algae such as dulse
and nori are a traditional part of
European and Asian cuisine and are used
to make certain other products like
agar and food additives.
Many red algae have multicellular
stages but these lack differentiated
tissues and organs. Unlike most other
algae, no cells with a flagellum are
found in any member of the group.
Unicellular forms typically live
attached to surfaces rather than
floating among the plankton, and both
the larger female and smaller male
gametes are non-motile, so that most
have a low chance of fertilization.
They have cell walls are made out of
cellulose and thick gelatinous
polysaccharides, which are the basis
for most of the industrial products
made from red algae.
The chloroplasts of red algae are bound
by a double membrane, like those of
green plants; both groups
(Archaeplastida) probably share a
common origin. Their plastids formed by
direct endosymbiosis of a
cyanobacteria, and in red algae are
pigmented with chlorophyll a and
various proteins called phycobilins,
which are responsible for their reddish
color. Other algae that lack
chlorophyll b appear to have acquired
their chloroplasts from red algae,
although their pigmentations are
somewhat different.
unicellular to multicellular (up to 1
m) mostly free-living but some
parasitic or symbiotic, with
chloroplasts containing phycobilins.
Cell walls made of cellulose with
mucopolysaccharides penetrated in many
red algae by pores partially blocked by
proteins (complex referred to as pit
connections). Usually with separated
phases of vegetative growth and sexual
reproduction. Common and widespread,
ecologically important, economically
important (source of agar). No
flagella. Ultrastructural identity:
Mitochondria with flat cristae,
sometimes associated with forming faces
of dictyosomes. Thylakoids single, with
phycobilisomes, plastids with
peripheral thylakoid. During mitosis,
nuclear envelope mostly remains intact
but some microtubules of spindle extend
from noncentriolar polar bodies through
polar gaps in the nuclear envelope.
Synapomorphy: No clear-cut feature
available; possibly pit connections
Composition: About 4,000 species.
CLASS Florideophyceae
CLASS Bangiophyceae
CLASS Rhodellophyceae
DOMAIN Eukaryota -
eukaryotes
KINGDOM Plantae Haeckel, 1866 -
plants
SUBKINGDOM Biliphyta
Cavalier-Smith, 1981
PHYLUM Rhodophyta
Wettstein, 1922 - red algae
SUBPHYLUM Rhodellophytina
Cavalier-Smith, 1998
CLASS
Rhodellophyceae Cavalier-Smith, 1998
SUBPHYLUM Macrorhodophytina
Cavalier-Smith, 1998
CLASS
Bangiophyceae
CLASS Florideophyceae
There is a debate as to if Rhodophyta
are plants or protists.
1. Red algae (phylum
Rhodophyta) are chiefly marine
multicellular algae that live in warmer
seawater.
2. They are generally much
smaller and more delicate that brown
algae.
3. Some are filamentous, but
most are branched, having a feathery,
flat, or ribbon-like appearance. (Fig.
30.7)
4. Coralline algae are red
algae with cell walls with calcium
carbonate; they contribute to coral
reefs.
5. Sexual reproduction involves
oogamy but the sperm are
non-flagellated.
6. Their chloroplasts resemble
cyanobacteria by containing chlorophyll
a and the pigment phycobilin.
7. The food
reserve (floridean starch) resembles
glycogen.
8. Like brown algae, red algae
are economically important.
a.
Mucilaginous material in cell walls is
source of agar used in drug capsules,
dental impressions, cosmetics.
b. In
the laboratory, agar is a major
microbiological media, and when
purified, is a gel for
electrophoresis.
c. Agar is used in food
preparation to keep baked goods from
drying and to set jellies and desserts.
The taxonomy of the algae is still in a
state of flux.
[1] Close-up of a red alga (Genus?
Laurencia), Class Florideophyceae,
Order=? a marine seaweed from Hawaii.
GNU
source: http://en.wikipedia.org/wiki/Ima
ge:Laurencia.jpg
[2] Bangia atropurpurea Profile:
unbranched filaments in tufts. Often
forming dense fringes in the spalsh
zone. Uniseriate at base, multiseriate
above with protoplasts separate in a
firm gelatinous sheath. Stellate
chloroplasts. US NOAA PD
source: http://www.glerl.noaa.gov/seagra
nt/GLWL/Algae/Rhodophyta/Cards/Bangia.ht
ml
is enslaved by a chromealveolate
eukaryote to form a plastid in the
chromealveolate. This kind of plastid
is presumably inherited by all other
chromalveolates (brown algae, diatoms,
water molds, Dinoflagellata,
Apicomplexa, ciliates) that have
plastids.
If this red alga endosymbiosis occured
only once, then all chromalveolates
with plastids inherited them and all
without lost them. Ciliates presumably
lost any inherited plastids.
(red algae) fossils (Bangiomorpha
pubescens) from Hunting Formation,
Somerset Island, arctic Canada.
This
is the oldest multicellular eukaryote
fossil and the oldest fossil of a
sexual species found yet.
[1] get images from Life on a Young
Planet, Knoll
source: Science 1990 vol 250
Butterfield N. J. A. H. Knoll K. Swett
1990 A bangiophyte red alga from the
Proterozoic of Arctic Canada. Science
250: 104-107[ISI][Medline]
[2] Figure 2. Griffithsia pacifica
(Florideophyceae). Electron micrograph
showing cytoplasm with numerous
chloroplasts (C) and starch (S). Starch
is the photosynthetic reserve and is
deposited free in the cytoplasm.
source: (American Journal of Botany.
2004;91:1494-1507.)
shows the protist and plant line
separating here at 1,230 mybn (first
plant).
"Microsporidia" evolves.
Ribosomal RNA shows
most ancient living fungi phylum
"Microsporidia" evolving now.
Microsporidia are parasites of animals,
now considered to be extremely reduced
fungi. Most infect insects, but they
are also responsible for common
diseases of crustaceans and fish, and
have been found in most other animal
groups, including humans and other
mammals which can be parasitized by
species of Encephalitozoon. Replication
takes place within the host's cells,
which are infected by means of
unicellular spores. These vary from
1-40 μm, making them some of the
smallest eukaryotes. They also have the
shortest eukaryotic genomes.
Microsporidia are unusual in lacking
mitochondria, and also lack motile
structures such as flagella. The spores
are protected by a layered wall
including proteins and chitin. Their
interior is dominated by a unique
coiled structure called a polar tube
(not to be confused with the polar
filaments of Myxozoa). In most cases
there are two closely associated
nuclei, forming a diplokaryon, but
sometimes there is only one.
Intracellular parasites, no
mitochondria, ribosomes are unusual in
being of prokaryotic size (70S) and
lacking characteristic eukaryotic 5.8S
ribosomal RNA as a separate molecule in
the microsporidia but is incorporated
into the 23S r RNA.
binucleate haploid?
During infection, the polar
tube penetrates the host cell (the
process has been compared by Patrick J.
Keeling to "turning a garden hose
inside out"), and the contents of the
spore are pumped through it. Keeling
likens the system to a combination of
"harpoon and hypodermic syringe",
adding that it is "one of the most
sophisticated infection mechanisms in
biology".
Once inside the host cell, the
sporoplasm grows, dividing or forming a
multinucleate plasmodium before
producing new spores. The
plasmodium divides by merogony to
produce merozoites that enter other
host cells, to repeat merogony, or to
undergo sporogony. The latter
parasites divide by binary fission to
produce numerous sporoblasts which
develop into spores.
The life cycle varies considerably.
Some have a simple asexual life cycle,
while others have a complex life cycle
involving multiple hosts and both
asexual and sexual reproduction.
Different types of spores may be
produced at different stages, probably
with different functions including
autoinfection (transmission within a
single host). The Microsporidia often
cause chronic, debilitating diseases
rather than lethal infections. Effects
on the host include reduced longevity,
fertility, weight, and general vigor.
Vertical transmission of microsporidia
is frequently reported.
Because they are unicellular,
Microsporidia were traditionally
treated as protozoa, and like other
amitochondriate eukaryotes were
considered to have diverged very early
on. However, other genes place them
alongside or within the Fungi, and this
is supported by several chemical and
morphological features. In particular
they appear to be allied with the
Zygomycota or Ascomycota.
Comparison of tubulin gene sequences
suggest that they are related to fungi;
hosts include most invertebrate phyla;
all classes of vertebrates, the
greatest number of species being known
from arthropods and fish; with growing
and dividing stages (meronts and
sporonts), and spores which are used
for transmission between hosts; meronts
with one nucleus or two closely
adhering and synchronously dividing
nuclei; with endoplasmic reticulum,
ribosomes and an atypical dictyosome
but no mitochondria, flagella, or
cytoskeletal structures; sporonts have
more abundant endoplasmic reticulum and
develop a surface coat which becomes
the outer layer of the spore wall;
spores unicellular with one or two
nuclei, a polar tube (polar filament),
the polaroplast and the posterior
vacuole; cytoplasm and nucleus (or
nuclei) become the infective agent
(sporoplasm), as it emerges from the
spore; meronts, ranging from small
rounded cells to plasmodia or
ribbon-like formations, divide
repeatedly by binary fission,
plasmotomy or multiple fission;
merogony is followed by sporogony, in
which cells known as sporonts are
committed to spore production;
sporonts, divide into sporoblasts, the
number of which is characteristic of
the genera; sporoblasts mature into
spores; but individual life cycles are
highly variable; meiosis occurs and
this indicates that gametogenesis and
fusion of gametes must occur but this
has been recognised for only a few
species; genera with an alternation of
diplokaryotic and monokaryotic stages
can be dimorphic and heterosporous.
Genus descriptions are usually based on
the type species.
DOMAIN Eukaryota - eukaryotes
KINGDOM Fungi
(Linnaeus, 1753) Nees, 1817 - fungi
PHYLUM Microsporidia (Balbiani, 1882)
Weiser, 1977
[1] Sporoblast of the Microsporidium
Fibrillanosema crangonycis. Electron
micrograph taken by Leon White. GNU
source: http://en.wikipedia.org/wiki/Ima
ge:Fibrillanosema_spore.jpg
[2] Spironema
multiciliatum Spironema:
Octosporoblastic sporogony producing
horseshoe-shaped monokaryotic spores in
sporophorous vesicles; monomorphic,
diplokaryotic and monokaryotic;
merogony - last generation merozoites
are diplokaryotic; sporogony - initial
division of the sporont nuclei is
meiotic as indicated by the occurrence
of synaptonemal complexes; spores are
horse-shoe-shaped, with swollen ends in
T. variabilis and have one elongate
nucleus; exospore with three layers,
endospore is of medium thickness;
polaroplast composed of two lamellar
parts, an anterior part of closely
packed lamellae and a posterior part of
wider compartments; polar tube is
isofilar and forms, in the posterior
quarter of the spore, 3-4 coils in a
single rank (T. variabilis) or 8-10
coils in a single rank (T. chironomi);
type species Toxoglugea vibrio in
adipose tissue of larvae of Ceratopogon
sp. (Diptera, Ceratopogonidae).
Spironema (spire-oh-knee-ma)
multiciliatum Klebs, 1893. Cells are
lanceolate, relatively flattened and
flexible. The cells have a spiral
groove, long kinetics and a tail, which
tapers posteriorly, and are about 15 -
21 microns without the tail. The
nucleus is located anteriorly or near
the centre of the cell. When the cells
are squashed, the cells are more
flexible. Food materials are seen under
the cell surface. Rarely observed.
This picture was taken by Won Je Lee
using conventional photographic film
using a Zeiss Axiophot microscope of
material collected in marine sediments
of Botany Bay (Sydney, Australia). The
image description refers to material
from Botany Bay. NONCOMMERCIAL USE
source: http://microscope.mbl.edu/script
s/microscope.php?func=imgDetail&imageID=
3928
shows the plant and fungi line
separating here at 1,000 mybn (first
fungi).
evolves.
Ribosomal RNA place fungi phylum
"Chytridiomycota" evolving now.
Many chytrids are haplodiploid
(alternate between haploid and diploid
cycles that both have mitosis).
Chytridiomycota is a division of the
Fungi kingdom and contains only one
class, Chytridiomycetes. The name
refers to the chytridium (from the
Greek, chytridion, meaning "little
pot"): the structure containing
unreleased spores.
The chytrids are the
most primitive of the fungi and are
mostly saprobic (feed on dead species,
degrading chitin and keratin). Many
chytrids are aquatic (mostly found in
freshwater). There are approximately
1,000 chytrid species, in 127 genera,
distributed among 5 orders. Both
zoospores and gametes of the chytrids
are mobile by their flagella, one
whiplash per individual. The thalli are
coenocytic and usually form no true
mycelium (having rhizoids instead).
Some species are unicellular.
DOMAIN
Eukaryota - eukaryotes
KINGDOM Fungi (Linnaeus,
1753) Nees, 1817 - fungi
PHYLUM
Chytridiomycota
CLASS Chytridiomycetes (De
Bary, 1863) Sparrow, 1958
Some chytrid species are known to kill
frogs in large numbers by blocking the
frogs' respiratory skins - the
infection is referred to as
chytridomycosis. Decline in frog
populations led to the discovery of
chytridomycosis in 1998 in Australia
and Panama. Chytrids may also infect
plant species; in particular,
maize-attacking and alfalfa-attacking
species have been described.
[1] Chytrids (Chytridiomycota): The
Primitive Fungi These fungi are
mostly aquatic, are notable for having
a flagella on the cells (a flagella is
a tail, somewhat like a tail on a sperm
or a pollywog), and are thought to be
the most primitive type of
fungi. actual photo comes
from: http://www.csupomona.edu/~jcclark
/classes/bot125/resource/graphics/chy_al
l_sph.html
source: http://www.davidlnelson.md/Cazad
ero/Fungi.htm
[2] Chytridiomycota - Blastocladiales
- zoospore of Allomyces (phase contrast
illumination) X 2000
source: http://www.mycolog.com/chapter2b
.htm
(Mesomycetozoea/DRIPs,
Choanoflagellates) evolves.
DOMAIN Eukaryota - eukaryotes
KINGDOM Protozoa
(Goldfuss, 1818) R. Owen, 1858 -
protozoa
SUBKINGDOM Sarcomastigota
(means=?)
PHYLUM Amoebozoa (Lühe, 1913)
Cavalier-Smith, 1998
PHYLUM Choanozoa
CLASS Choanoflagellatea
(Choanoflagellates)
CLASS Corallochytrea
CLASS
Mesomycetozoea Mendoza et al., 2001
(DRIPs)
CLASS Cristidiscoidea
(DRIPs) evolve.
The Mesomycetozoea or
DRIP clade are a small group of
protists, mostly parasites of fish and
other animals. One species,
Rhinosporidium seeberi, infects birds
and mammals, including humans. They are
not particularly distinctive
morphologically, appearing in host
tissues as enlarged spheres or ovals
containing spores, and most were
originally classified in various groups
of fungi, protozoa, and algae. However,
they form a coherent group on molecular
trees, closely related to both animals
and fungi and so of interest to
biologists studying their origins.
The name DRIP is an acronym for the
first protozoa identified as members of
the group - Dermocystidium, the rosette
agent, Ichthyophonus, and
Psorospermium. Cavalier-Smith later
treated them as the class
Ichthyosporea, since they were all
parasites of fish. Since other new
members have been added, Mendoza et al.
suggested changing the name to
Mesomycetozoea, which refers to their
evolutionary position. Note the name
Mesomycetozoa (without a second e) is
also used to refer to this group, but
Mendoza et al. use it as an alternate
name for the phylum Choanozoa.
Assemblage identified from molecular
studies, mostly pathogens, a few
genera, no synapomorphy. Grouping
formalized by Herr, Ajello, Taylor,
Arseculeratne & Mendoza, 1999.
DOMAIN
Eukaryota - eukaryotes
KINGDOM Protozoa
(Goldfuss, 1818) R. Owen, 1858 -
protozoa
SUBKINGDOM Sarcomastigota
(means=?)
PHYLUM Amoebozoa (Lühe, 1913)
Cavalier-Smith, 1998
PHYLUM Choanozoa
CLASS Choanoflagellatea
(Choanoflagellates)
CLASS Corallochytrea
CLASS
Mesomycetozoea Mendoza et al., 2001
(DRIPs)
CLASS Cristidiscoidea
[1] Ichthyophonus, a fungus-like
protistan that occurs in high
prevalence in Pacific Ocean perch
(Sebastes aultus) and yellowtail
rockfish (Sebastes flavedus). Note the
parasite forms branching hyphae-like
structures. Ichthyophonus hoferi has
caused massive mortalities in herring
in the Atlantic ocean, and has recently
been reported to cause disease in wild
Pacific herring from Washington through
Alaska. COPYRIGHTED EDU
source: http://oregonstate.edu/dept/salm
on/projects/images/16Ichthyophonus.jpg
[2] Microscopic appearence of the
organism is dependent on its stage of
development. The stages include (1)
spore at ''resting'' stage, (2)
germinating spore, (3) hyphal
stage. It is believed that there are
two forms of Ichthyophonus, both
belonging to one genus. One of them is
known as the ''salmon'' form, occuring
in freshwater and cold-preferring sea
fishes: this form is characterized by
its ability to produce long tubulose
germ hyphae. The other is called the
''aquarium fish'' form, typical of the
tropical freshwater fishes. This form
is completely devoid of hyphae.
Developmental cycle of Ichthyophonus
hoferi: 1-5 - development of
''daughter'' spores, 7-11 - development
of resting spore from the ''daughter''
spore, 12-19 - development of resting
spore by fragmentation. COPYRIGHTED
source: http://www.fao.org/docrep/field/
003/AC160E/AC160E02.htm
a period of dramatic global change and
quickening reef evolution. The
appearance of heavily calcified
microbial elements (calcimicrobes; e.g.
Girvanella and Renalcis) in the Tonian
(1.0-0.85Ga), coincident with the
disappearance of conical elements and
decline in stromatolites, is a critical
event.
evolve in unicellular eukaryote living
objects. This is the first proto eye.
The
eye spot probably evolved from a
plastid, and plastids may have only
formed symbiotic relationships in
euglenozoa much later, since the
plastids in euglenozoa are enclosed in
3 membranes (the same as chloroplasts
in plants), they are thought to have
been formed from captured green algae
which evolve much later.
shows the fungi and pseudocoeles lines
separating here at 965 mybn (first
pseudocoel and first animal).
"Choanoflagellates" and "Acanthoecida"
evolve.
The choanoflagellates are a
group of flagellate protozoa. They are
considered to be the closest relatives
of the animals, and in particular may
be the direct ancestors of sponges.
Each choanoflagellate has a single
flagellum, surrounded by a ring of
hairlike protrusions called microvilli,
forming a cylindrical or conical collar
(choanos in Greek). The flagellum pulls
water through the collar, and small
food particles are captured by the
microvilli and ingested. It also pushes
free-swimming cells along, as in animal
sperm, whereas most other flagellates
are pulled by their flagella.
Most choanoflagellates are sessile,
with a stalk opposite the flagellum. A
number of species are colonial, usually
taking the form of a cluster of cells
on a single stalk. Of special note is
Proterospongia, which takes the form of
a glob of cells, of which the external
cells are typical flagellates with
collars, but the internal cells are
non-motile.
The choanocytes (also known as
"collared cells") of sponges have the
same basic structure as
choanoflagellates. Collared cells are
occasionally found in a few other
animal groups, such as flatworms. These
relationships make colonial
choanoflagellates a plausible candidate
as the ancestors of the animal kingdom.
DOMAIN Eukaryota - eukaryotes
KINGDOM Protozoa
(Goldfuss, 1818) R. Owen, 1858 -
protozoa
SUBKINGDOM Sarcomastigota
(means=?)
PHYLUM Amoebozoa (Lühe, 1913)
Cavalier-Smith, 1998
PHYLUM Choanozoa
CLASS Choanoflagellatea
(Choanoflagellates and Acanthoecida)
ORDER
Choanoflagellida W.S. Kent, 1880 -
(Choanoflagellates)
ORDER Acanthoecida
CLASS
Corallochytrea
CLASS Mesomycetozoea Mendoza et
al., 2001 (DRIPs)
CLASS Cristidiscoidea
Also identified in the Phylum Choanozoa
are the Ichthyosporea.
[1] DOMAIN Eukaryota - eukaryotes
KINGDOM Protozoa (Goldfuss, 1818) R.
Owen, 1858 - protozoa SUBKINGDOM
Sarcomastigota (means=?) PHYLUM
Choanozoa CLASS
Choanoflagellatea (Choanoflagellates
and Acanthoecida) ORDER
Acanthoecida Saepicula: Cells
solitary, lorica funnel-shaped, 2
chambers delimited by a waist;
constructed of rod-shaped costal
strips; posterior chamber obconical
with 2 series of costae located more or
less regularly around chamber, one
series almost parallel to the long axis
of cell and second series almost
perpendicular to long axis; anterior
chamber formed by ring of equally
spaced longitudinal costae surmounted
by single transverse costa; marine
This image is based on a drawing
provided by Won Je Lee. NONCOMMERCIAL
USE
source: http://microscope.mbl.edu/script
s/microscope.php?func=imgDetail&imageID=
3229
[2] Choanoeca: Cells solitary with
distinct, firm flask-shaped theca more
or less closely investing protoplast,
with short pedicel; collar relatively
long, widely expanded; flagellum absent
in adult, but produced prior to cell
division for locomotory use by juvenile
cell; in marine and brackish habitats,
frequently attached to filamentous
algae and hydrozoa Choanoeca
(ko-an-o-eek-a), an unusual loricate
collar flagellate (choanoflagellate) in
that the usual form is without a
flagellum. Flagellated motile stage is
occasionally produced. Widely dispersed
pseudopodial elements of the collar are
evident in this image. Differential
interference contrast. This picture
was taken by David Patterson and Aimlee
Laderman of material collected from a
freshwater Atantic white cedar swamp at
Cumloden near Woods Hole in
Massachusetts, USA in spring and
summer, 2001. NONCOMMERCIAL USE
source: http://microscope.mbl.edu/script
s/microscope.php?func=imgDetail&imageID=
170
multicellularity evolves, where a
zygote produces differentiated cells
that stick together to form one
organism.
Metazoan multicellularity appears to
be different from colonialism (where
independent cells of the same species
work together and function as one
unit), because one zygote produces all
the cells in the organism.
evolve. Metazoans are multicellular,
but their cells perform different
functions and originate from one
cell(?). This is`also the beginning of
the Animal Subkingdom "Radiata",
species with radial symmetry. These are
the sponges. There are only 3 kinds of
metazoans: sponges, cnidarians, and
bilaterians (which include all insects
and vertibrates). Sponges are the
first organisms whose DNA codes for
more than one kind of cell. Sponges
have 3 different cell types. Some
cells form a body wall, some digest
food, some form a skeletal frame.
All sponge
cells are totipotent and are capable of
regrowing a new sponge.
The two major
subkingdoms of the Kingdom Animalia are
Radiata (the radiates) and Bilateria
(the bilaterians).
[1]
source: http://www.museums.org.za/bio/me
tazoa.htm
[2]
source: http://www.museums.org.za/bio/me
tazoa.htm
evolve. These genes regulate the
building of major body parts.
division "Zygomycota" (bread molds, pin
molds, microsporidia,...) evolving now.
[1] Figure 2. Zygomycota A: sporangia
of Mucor sp. B: whorl of sporangia of
Absidia sp. C: zygospore of
Zygorhynchus sp. D: sporangiophore and
sporangiola of Cunninghamella sp.
source: http://www.botany.utoronto.ca/Re
searchLabs/MallochLab/Malloch/Moulds/Cla
ssification.html
[2] Figure 3. Syncephalis, a member
of the Zygomycota parasitic on other
Zygomycota
source: http://www.botany.utoronto.ca/Re
searchLabs/MallochLab/Malloch/Moulds/Cla
ssification.html
Placozoans
look like amoebas but are
multicellular.
There is only one known species,
"Tricoplax adhaerens", and one other
potential species "Tricoplax reptans"
in the entire Placozoa phylum.
Putative eggs have been observed, but
they degrade at the 32-64 cell stage.
Neither embryonic development nor sperm
have been observed, however Trichoplax
genomes show evidence of sexual
reproduction. Asexual reproduction by
binary fission is the primary mode of
reproduction observed in the lab.
The haploid number of chromosomes is
six. It has the smallest amount of DNA
yet measured for any animal with only
50 megabases (80 femtograms per cell).
A trichoplax genome project is
currently underway.
DOMAIN Eukaryota -
eukaryotes
KINGDOM Animalia Linnaeus, 1758 -
animals
SUBKINGDOM Radiata (Linnaeus, 1758)
Cavalier-Smith, 1983 - radiates
INFRAKINGDOM Placozoa Cavalier-Smith,
1998
PHYLUM Placozoa Grell, 1971
jellies) evolves.
DOMAIN Eukaryota - eukaryotes
KINGDOM Animalia
Linnaeus, 1758 - animals
SUBKINGDOM Radiata
(Linnaeus, 1758) Cavalier-Smith, 1983 -
radiates
INFRAKINGDOM Coelenterata
Leuckart, 1847
PHYLUM Ctenophora
Eschscholtz, 1829 - comb jellies
CLASS Tentaculata
CLASS Nuda
division "Glomeromycota" (Arbuscular
mycorrhizal fungi) evolving now.
[1] germinating Gigaspora decipiens
source: http://pages.unibas.ch/bothebel/
people/redecker/ff/glomero.htm
[2] Archaeospora leptoticha spores
source: http://pages.unibas.ch/bothebel/
people/redecker/ff/glomero.htm
jellyfish evolves. Jellyfish have
photon detecting cells and a lens made
of ?.
the phylum "Basidiomycota" (most
mushrooms, rusts, club fungi) evolve.
Genetic
comparison shows the second largest
group of Fungi, the phylum
"Basidiomycota" (most mushrooms, rusts,
club fungi) evolving now.
The Division Basidiomycota is a large
taxon within the Kingdom Fungi that
includes those species that produce
spores in a club-shaped structure
called a basidium. Essentially the
sibling group of the Ascomycota, it
contains some 30,000 species (37% of
the described fungi)
[1] Amanita muscaria
(Homobasidiomycetes)
source: http://en.wikipedia.org/wiki/Ima
ge:Agaricales.jpg
[2] Basidiomycete Life Cycle tjv
source: http://botit.botany.wisc.edu/ima
ges/332/Basidiomycota/General_basidio/Ba
sidiomycete_Life_Cycle_tjv.php?highres=t
rue
"Ascomycota" (yeasts, truffles,
Penicillium, morels, sac fungi)
evolves.
Genetic comparison shows the largest
Fungi phylum "Ascomycota" (yeasts,
truffles, Penicillium, morels, sac
fungi) evolving now.
47,000 described
species.
[1] white truffle
cutted photographed by
myself GNU head Permission is
granted to copy, distribute and/or
modify this document under the terms of
the GNU Free Documentation License,
Version 1.2 or any later version
published by the Free Software
Foundation; with no Invariant Sections,
no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is
included in the section entitled ''Text
of the GNU Free Documentation
License.''
source: http://upload.wikimedia.org/wiki
pedia/commons/f/fd/Truffle_washed_and_cu
tted.jpg
[2] EColi-Scerevisiae.jpg (50KB, MIME
type: image/jpeg) Wikimedia Commons
logo This is a file from the Wikimedia
Commons. The description on its
description page there is shown
below. Escherichia coli (little
forms) & Saccharomyces cerevisiae (big
forms) by MEB Public domain This file
has been released into the public
domain by the copyright holder, its
copyright has expired, or it is
ineligible for copyright. This applies
worldwide. brewer's yeast/baker's
yeast
source: http://en.wikipedia.org/wiki/Ima
ge:EColi-Scerevisiae.jpg
largest and second largest lines of
Fungi (Ascomycota and Basidiomycota)
splitting now.
of Ascomycota Fungi called
"Archaeascomycetes" (fission yeast,
pneumonia fungus) evolving now.
shows the pseudocoel and schizocoel
lines separating here at 675 mybn
(first schizocoel).
mybn).
Ascomycota Fungi "Hemiascomycetes"
evolving now.
symmetry) species evolves. Animal
phylum Acoelomorpha (acoela flat worms
and nemertodermatida) evolves.
This
begins the Subkingdom "Bilateria".
lack
a digestive track, anus and coelom.
DO
MAIN Eukaryota - eukaryotes
KINGDOM Animalia
Linnaeus, 1758 - animals
SUBKINGDOM
Bilateria (Hatschek, 1888)
Cavalier-Smith, 1983 - bilaterians
PHYLUM
"Acoelomorpha" - acoelomorphs
ORDER Acoela
- acoels
ORDER Nemertodermatida -
nemertodermatids
[1] Convoluta pulchra Smith and Bush
1991, a typical mud-inhabiting acoel
that feeds on diatoms
source: ?
"Ustilaginomycetes" (corn smut fungus)
and "Hymenomycetes" (white rot fungus)
evolve.
Genetic comparison shows the
Basidiomycota Fungi "Ustilaginomycetes"
(corn smut fungus) and "Hymenomycetes"
(white rot fungus) evolving now.
mybn).
evolve at this time. Protostomes
include the 3 infrakingdoms Ecdysozoa
(a variety of worms and the arthropods
{a huge group including all insects and
crustaceans}), Platyzoa (rotifers and
flatworms), and Lophotrochozoa
(brachiopods {clams}, molluscs
{snails}, and a variety of worms).
Doushantuo formation in China.
Vernanimalcula, 178 um in length, from
Doushantuo Formation, China. First
fossil of organism with bilateral
symmetry, mouth, digestive track, gut
and anus.
[1] Fig. 2. Close-up images of
prominent anatomical features of
Vernanimalcula guizhouena. The scale
bar represents 18 µm in (A), 32 µm in
(B), 24 µm in (C), and 28 µm in (D).
SO, sensory organ, i.e., external pit;
LU, lumen; PH, pharynx; MO, mouth; CO,
coelomic lumen; CW, mesodermal coelomic
wall; GU, gut. (A) Detail of collared
mouth, multilayered pharynx, and one
anterior surface pit. In this image,
which is from the holotype specimen
(Fig. 1A), the floor of the pit can be
seen to be composed of a specialized
concave layer. Note the coelomic wall,
which here as elsewhere in these
specimens has a thickness of about 5 to
6 µm. (B) Mouth of a fourth specimen,
Q3105, displaying collared mouth and
pharynx, ventral view. (C) Lumen of
pharynx from a fifth specimen, X10419,
secondarily encrusted but revealing
morphology of opening of pharynx into
gut similar to that seen in the
specimens shown in Fig. 1. (D) Close-up
of spaced external pits, interpreted as
possible sensory organs, from the same
specimen as shown in Fig. 1B [compare
(A)].
source: http://www.sciencemag.org/cgi/co
ntent/full/sci;305/5681/218
[2] Fig. 1. Images of three
different, fairly well preserved
specimens of the bilaterally organized
fossil animal Vernanimalcula
guizhouena. Left panels show digitally
recorded, transmitted light images of
sections about 50 µm thick, which had
been ground from larger rock samples,
mounted on slides, and viewed through a
light microscope. Right panels show
color-coded representations of the
images on the left. These were prepared
by digital image overlay. Yellow,
external ectodermal layer; ochre,
coelomic mesodermal layer; red, surface
pits; mauve, pharynx; light tan,
endodermal wall of gut; gray-green,
lumen of mouth; dark gray, paired
coelomic cavities; lighter gray, lumen
of gut; brown, ''gland-like''
structures, with central lumen (B);
light green, mineral inclusions (C).
The scale bar represents 40 µm in (A),
55 µm in (B), and 46 µm in (C). (A)
Holotype specimen, X00305, slightly
tilted, almost complete ventral level
coronal section, passing through the
ventrally located mouth. (B) Coronal
section of second specimen, X08981,
passing through dorsal wall of pharynx
and displaying complete A-P length of
digestive tract, including posterior
end [not visible in (A)]. (C) Tilted
coronal section of third specimen,
X10475, possibly slightly squashed,
passing through dorsal wall of pharynx
and through the dorsal wall of the gut.
For dimensions, see Table 1.
source:
evolves. Ecdysozoa are animals that
molt (lose their outer skins) as they
grow.
Ecdysozoa include:
the Phylum "Chaetognatha"
(Arrow Worms),
the Superphylum
"Aschelminthes", containing the 5
Phlya:
"Kinorhyncha" (kinorhynchs)
"Loricifera"
(loriciferans)
"Nematoda" (round worms)
"Nematomorpha"
(horsehair worms),
"Priapulida" (priapulids)
the
Superphlyum "Panarthropoda" containing
the 3 Phyla:
"Arthropoda" (arthropods:
insects, shell fish)
"Onychophora"
(onychophorans)
"Tardigrada" (tardigrades)
evolve on Jellyfish(?).
fauna near Adelaide, Australia.
nervous system evolves in bilaterians.
in early bilaterians.
beginning of the Subkingdom
Deuterostomia and Infrakingdom
"Coelomopora" (Ambulacraria) with the
two Phyla "Hemichordata" (acorn worms)
and "Echinodermata" (sea cucumbers, sea
urchins, starfish).
DOMAIN Eukaryota - eukaryotes
KINGDOM Animalia
Linnaeus, 1758 - animals
SUBKINGDOM
Bilateria (Hatschek, 1888)
Cavalier-Smith, 1983 - bilaterians
BRANCH
Deuterostomia Grobben, 1908 -
deuterostomes
PHYLUM Vetulicolia Shu et
al., 2001
INFRAKINGDOM Coelomopora
(Marcus, 1958) Cavalier-Smith, 1998
INFRAKINGDOM Chordonia (Haeckel, 1874)
Cavalier-Smith, 1998
(Arrow Worms) evolves.
Hemichordonia (acorn worms) evolves.
DOMAIN Eukaryota - eukaryotes
KINGDOM Animalia
Linnaeus, 1758 - animals
SUBKINGDOM
Bilateria (Hatschek, 1888)
Cavalier-Smith, 1983 - bilaterians
BRANCH
Deuterostomia Grobben, 1908 -
deuterostomes
PHYLUM Vetulicolia Shu et
al., 2001
INFRAKINGDOM Coelomopora
(Marcus, 1958) Cavalier-Smith, 1998
PHYLUM Echinodermata Klein, 1734 ex
De Brugière, 1789 - echinoderms
PHYLUM
Hemichordata (Bateson, 1885) auct. -
hemichordates
Echinodermata (sea cucumbers, sea
urchins, sand dollars, star fish)
evolves.
DOMAIN Eukaryota - eukaryotes
KINGDOM Animalia
Linnaeus, 1758 - animals
SUBKINGDOM
Bilateria (Hatschek, 1888)
Cavalier-Smith, 1983 - bilaterians
BRANCH
Deuterostomia Grobben, 1908 -
deuterostomes
PHYLUM Vetulicolia Shu et
al., 2001
INFRAKINGDOM Coelomopora
(Marcus, 1958) Cavalier-Smith, 1998
PHYLUM Echinodermata Klein, 1734 ex
De Brugière, 1789 - echinoderms
PHYLUM
Hemichordata (Bateson, 1885) auct. -
hemichordates
blood cells evolve in bilaterian worms.
Superphylum Gnathifera {gnathiferans},
Phylum Gastrotricha {gastrotrichs}, and
Phylum Platyhelminthes {flatworms})
evolve.
evolves. Chordata is a very large
group that contains all fish,
amphibians, reptiles and mammals.
DOMAIN Eukaryota - eukaryotes
KINGDOM Animalia
Linnaeus, 1758 - animals
SUBKINGDOM
Bilateria (Hatschek, 1888)
Cavalier-Smith, 1983 - bilaterians
BRANCH
Deuterostomia Grobben, 1908 -
deuterostomes
INFRAKINGDOM Chordonia
(Haeckel, 1874) Cavalier-Smith, 1998
PHYLUM Chordata Bateson, 1885 -
chordates
SUBPHYLUM Tunicata Lamarck,
1816 - tunicates
SUBPHYLUM
Cephalochordata - lancelets
SUBPHYLUM
Vertebrata Cuvier, 1812 - vertebrates
Tunicata (tunicates {sea squirts})
evolves.
DOMAIN Eukaryota - eukaryotes
KINGDOM Animalia
Linnaeus, 1758 - animals
SUBKINGDOM
Bilateria (Hatschek, 1888)
Cavalier-Smith, 1983 - bilaterians
BRANCH
Deuterostomia Grobben, 1908 -
deuterostomes
INFRAKINGDOM Chordonia
(Haeckel, 1874) Cavalier-Smith, 1998
PHYLUM Chordata Bateson, 1885 -
chordates
SUBPHYLUM Tunicata Lamarck,
1816 - tunicates
SUBPHYLUM
Cephalochordata - lancelets
SUBPHYLUM
Vertebrata Cuvier, 1812 - vertebrates
oxygen from water through a digestive
system, evolves in segmented worms.
Ediacaran fossil.
[1] from adelaide, australia
source: http://news.bbc.co.uk/1/hi/sci/t
ech/3208583.stm
Ashelminthes (round worms, horsehair
worms, priapulids) and Pananthropoda
(arthropods, onychophorans,
tardigrades) separate.
Cephalochordata (lancelets) evolves.
This is the first fish.
DOMAIN Eukaryota - eukaryotes
KINGDOM Animalia
Linnaeus, 1758 - animals
SUBKINGDOM
Bilateria (Hatschek, 1888)
Cavalier-Smith, 1983 - bilaterians
BRANCH
Deuterostomia Grobben, 1908 -
deuterostomes
INFRAKINGDOM Chordonia
(Haeckel, 1874) Cavalier-Smith, 1998
PHYLUM Chordata Bateson, 1885 -
chordates
SUBPHYLUM Tunicata Lamarck,
1816 - tunicates
SUBPHYLUM
Cephalochordata - lancelets
SUBPHYLUM
Vertebrata Cuvier, 1812 - vertebrates
shows the chordate line separating from
echinoderm line here at 550 mybn (first
chordates).
"Ashelminthes" evolves. This includes
the 5 Phyla:
Kinorhyncha (kinorhynchs),
Loricifera (loriciferans),
Nematoda (round worms),
Nematomorpha
(horsehair worms),
Priapulida (priapulids).
DOMAIN Eukaryota - eukaryotes
KINGDOM Animalia
Linnaeus, 1758 - animals
SUBKINGDOM
Bilateria (Hatschek, 1888)
Cavalier-Smith, 1983 - bilaterians
BRANCH
Protostomia Grobben, 1908 -
protostomes
INFRAKINGDOM Ecdysozoa
Aguinaldo et al., 1997 ex
Cavalier-Smith, 1998 - ecdysozoans
SUPERPHYLUM Aschelminthes
PHYLUM Priapulida Théel, 1906 -
priapulids
PHYLUM Kinorhyncha
Reinhard, 1887 - kinorhynchs
PHYLUM
Loricifera Kristensen, 1983 -
loriciferans
PHYLUM Nematoda (Rudolphi,
1808) Lankester, 1877 - round worms
PHYLUM Nematomorpha Vejdovsky, 1886 -
horsehair worms
evolves. This includes the 5 Phyla:
Gna
thostomulida (gnathostomulids),
Cycliophora
(cycliophorans),
Micrognathozoa,
Rotifera (rotifers),
Acanthocephala
(acanthocephalans).
DOMAIN Eukaryota - eukaryotes
KINGDOM Animalia
Linnaeus, 1758 - animals
SUBKINGDOM
Bilateria (Hatschek, 1888)
Cavalier-Smith, 1983 - bilaterians
BRANCH
Protostomia Grobben, 1908 -
protostomes
INFRAKINGDOM Platyzoa
Cavalier-Smith, 1998
SUPERPHYLUM
Gnathifera - gnathiferans
PHYLUM
Gnathostomulida (Ax, 1956) Riedl, 1969
- gnathostomulids
PHYLUM Cycliophora Funch
& Kristensen, 1995 - cycliophorans
PHYLUM
Micrognathozoa (Kristensen & Funch,
2000)
PHYLUM Rotifera Cuvier,
1798 - rotifers
PHYLUM
Acanthocephala Kohlreuther, 1771 -
acanthocephalans
Lophotrochozoa evolves. This includes
brachiopods, bryozoans, clams, squids
and octopuses (cephalopods), and
snails.
This infrakingdom is made of:
Superphylum
Lophophorata,
Phylum Bryozoa (bryozoans),
Phylum Entoprocta
(entoprocts),
Superphylum Eutrochozoa.
DOMAIN Eukaryota -
eukaryotes
KINGDOM Animalia Linnaeus, 1758 -
animals
SUBKINGDOM Bilateria (Hatschek,
1888) Cavalier-Smith, 1983 -
bilaterians
BRANCH Protostomia Grobben, 1908
(protostomes)
INFRAKINGDOM "Lophotrochozoa"
(lophotrochozoans)
SUPERPHYLUM Lophophorata
PHYLUM
Bryozoa Ehrenberg, 1831 (bryozoans)
PHYLUM Entoprocta (Nitsche, 1869)
(entoprocts)
SUPERPHYLUM Eutrochozoa
Lophophorata evolves. This includes
the two Phyla Phoronida (phoronids) and
Brachiopoda (brachiopods {clams,
oysters, muscles}).
DOMAIN Eukaryota - eukaryotes
KINGDOM Animalia
Linnaeus, 1758 - animals
SUBKINGDOM
Bilateria (Hatschek, 1888)
Cavalier-Smith, 1983 - bilaterians
BRANCH
Protostomia Grobben, 1908
(protostomes)
INFRAKINGDOM "Lophotrochozoa"
(lophotrochozoans)
SUPERPHYLUM Lophophorata
PHYLUM Phoronida (phoronids)
PHYLUM
Brachiopoda (brachiopods)
(phoronids) evolves.
DOMAIN Eukaryota - eukaryotes
KINGDOM Animalia
Linnaeus, 1758 - animals
SUBKINGDOM
Bilateria (Hatschek, 1888)
Cavalier-Smith, 1983 - bilaterians
BRANCH
Protostomia Grobben, 1908
(protostomes)
INFRAKINGDOM "Lophotrochozoa"
(lophotrochozoans)
SUPERPHYLUM Lophophorata